This is an in-progress cleaned version of the final PR (numberscope#361) of
  the Delft student user interface project, which it supersedes.

  Comments from the original PR that remain relevant:
  * The end-to-end tests run using Firefox and Chromium.
  * New tests are in the e2e folder.
  * The tests often depend on specific classes and IDs, so they may
    need to be updated upon changes to Numberscope.
  * The tests can be executed as the following npm script:
    `npm run test:e2e`
  * An interactive testing UI and debugger can be executed as the
    following npm script: `npm run test:e2e:ui`

  Caveats concerning trying this cleaned PR and its status:
  * Make certain to run `npm install` after pulling this PR.
  * Many of the tests do not yet pass, perhaps because of the "specific
    classes and IDs" point mentioned above and the fact that ui2 has
    diverged significantly from the Delft PR series.
  * Tests are not yet run automatically prior to commit.
  * I do not think there are any image tests yet, we need to try to add
    them.
  * Tests are not yet performed in the continuous integration checks
    to be run on GitHub; they should be.

  The strong desire for image tests led to a cascade of changes in this
  commit, mostly driven by the need to have reproducible images:

  - Removes all use of `sketch.noLoop()` and `sketch.loop()` in favor
    of the previously existing `stop()` and `continue()` visualizer methods,
    to allow:
  - Adds a `frames=NNN` query parameter to URLs to set the maximum number
    of frames a visualization may draw
  - Switches from the "static" instance of mathjs to a "dynamic" one, to
    allow its random number configuration to be controlled. In conjunction
    with this, moves all math functions into a single math module, as
    extensions of mathjs.
  - Removes all use of `Math.random()` in favor of the mathjs random
    generator
  - Adds a `randomSeed=AAAA` query parameter to URLs to make the mathjs
    random generator reproducible.
  - Documents all of the above changes.

  Also adds new tests for `src/shared/defineFeatured.ts` and corrects
  the documentation extraction facility for the package manager
  scripts.

  Resolves numberscope#25.
  Resolves numberscope#73.
  Resolves numberscope#246.

   In other words, it should never call calculate twice for the
   same index. This is tested by 10K random accesses to indices
   less than 1M, followed by accessing the first 10K entries,
   followed by accessing the last 10K entries. Hopefully that
   should suffice.

   Resolves numberscope#54.

  This is an initial pass at addressing numberscope#113.
  Note, however, that ModFill is not reporting to the person doing
  visualization that it is running with different parameter values
  than shown. So that still must be done, but for that part we will need
  a resolution to numberscope#112, which will be a sufficiently involve change that
  we should leave it to a spearate PR from this numberscope#420.

  Resolves numberscope#174.

  Resolves numberscope#219.

  Resolves numberscope#226.

  Resolves numberscope#292.

  Resolves numberscope#217

  Use a list of "stressful sequences" to perform at least two image tests on
  each visualizer. As this change uncovered several existing errors, there
  are numerous other changes in this commit to return to a state of all tests
  passing. Here is an enumeration of other changes, in no particular order:

  * Change husky pre-commit actions so that the end-to-end tests are not
    run if there is an existing successful test since any files in the project
    last changed.
  * On most image tests, snapshot only the visualizer canvas.
  * Make 'axios' a runtime dependency, rather than just development, as it
    is used when obtaining OEIS sequence values in the running frontend.
  * So many other changes are made to Histogram.ts that this PR also adds
    hatching to show the elements with unknown factorization. Adds the
    "p5.brush" package to draw the hatching. Since this necessitates WebGL,
    adds a new 'P5GLVisualizer' base class for visualizers that wish to use
    a WebGL canvas.
  * Updates several dependencies to latest to make sure their out-of-dateness
    was not contributing to test issues.
  * Switches to the (ES) "module" import system from "commonjs" to ensure
    that was not contributing to test issues.

Resolves numberscope#294.

  * Specifies font locations in a way that vite understands how to
    relocate in both the 'dev' and 'build' versions of the app.
  * Properly marks both factor cache and value cache as empty at the
    initialization of an OEIS sequence.
  * Allows ±Infinity as valid values of INTEGER param fields for convenience.
  * Allows specimenQuery to take the output of parseSpecimenQuery to
    recreate the same specimen query as was parsed, for the sake of testing.
  * Turns off the browser default context menu on visualizers, which wasn't
    particularly useful and was interfering with the UI for some visualizers.
  * Fixes typos in Differences visualizer (this.first -> sequence.first)
  * Makes FactorHistogram visualizer a p5 WebGL-based visualizer, and adds
    hatching to the "0 factors" bar to indicate the terms with unknown
    factorizations.
  * Uses the WebGL default controls to implement panning, zooming, and (rather
    uselessly but somewhat spectacularly) rotating the plot in three
    dimensions for the FactorHistogram visualizer.
  * On FactorHistogram's first pass over the sequence data, collects the
    counts for each possible number of factors, as opposed to the number
    of factors for each entry, to avoid a possibly disastrously long loop
    on the second pass that accumulates bin counts. This also streamlines
    the computation of the largest number of factors in the data.
  * Factors out repeated code in FactorHistogram, for labeling bars and
    displaying text.
  * Fits the hover box in FactorHistogram to the text to be displayed.
  * FactorHistogram displays a temporary message if factoring is taking a
    long time.
  * Moves the bar labels of FactorHistogram just under their respective bars,
    to make sure they are visible.
  * Selects y-axis ticks at round numbers for FactorHistogram, and moves the
    tick labels closer to their ticks.
  * Prevents FactorHistogram from looping except when there is mouse activity.
  * Prevents ModFill from freezing up if too large a "mod dimension" is
    chosen. Note TODO: display a warning when a smaller mod dimension than
    requested is actually used.
  * Prevents Vue's reactivity system from attempting to modify the behavior
    of p5 sketches, using the Vue `markRaw` method. This change prevents
    some instances of infinite loops caused by cascading change notifications.
  * Tightens up the typing of P5Visualizer so that it is possible to derive
    another visualizer base class P5GLVisualizer from it. Also splits up the
    inhabit method so that P5GLVisualizer can modify it as needed.
  * Allow negative start indices for Show Factors visualizer.
  * Show at most 100 terms in Show Factors (no room on screen for more than
    that).
  * Updates TypeScript target versions of JavaScript

Resolves numberscope#226.

…archy

  All params for controlling which terms of a sequence will be used in
  the visualization are removed from individual visualizers. Instead, there
  are uniform params in the Sequence classes themselves.

  Resolves numberscope#411.

  In this implementation, several other changes are necessary and/or
  expedient to make. In particular, the type of sequence indices is changed
  to bigint and bounds to ExtendedBigint (the union of bigint and ±Infinity),
  in preparation for addressing numberscope#455. Additional changes include:

  * Removal of SequenceDefault class, as everything now derives from Cached.
  * More care in caching of OEIS sequences, to provide some help with numberscope#459.
  * Individual-parameter validation functions now take a validation status
    to update based on the finding. This refactor avoids a frequent need to
    merge status objects.
  * Individual-parameter validation functions are called in a context
    of `this` set to the Paramable object, so that other data from the
    paramable can be accessed.
  * New `math` functions for dealing with ExtendedBigints.
  * NumberGlyph visualizer now tries to display as many terms as are
    available and will fit on the screen, except in case there are infinitely
    many terms available, in which case it still defaults to 64 terms. This
    change is needed so that the general length parameter for Sequences would
    affect what NumberGlyph displayed.
  * Puts reactivation of "known" OEIS sequences into a function
    rather than at top level of sequences.ts so that the timing of
    when it occurs can be controlled.
  * Renames property `_size` of P5Visualizer to `size` as multiple derived
    classes seem to need this value (i.e., not just used internally in the base
    class).
  * Makes sure the p5 loop is restarted if need be every time `.show()` is
    called on a visualizer.
  * Temporarily disables A000521 transversal tests until we can
    get incremental OEIS loading to work.
  * Adds a test for starting a visualization deep into a sequence.

…al one

  Unfortunately, due to the intricacies of end-to-end testing with image
  comparison, this is a very large commit. It introduces running tests
  in a Docker container for the sake of reproducibility. (So note that
  henceforth you must have docker installed and running on your machine to
  perform testing, and hence to make a commit.)

  However, it turns out not all tests can be run in a Docker container --
  Firefox is not able to supply a WebGL context inside of Docker. Hence,
  some tests still need to be run directly on the host machine.

  To deal with all this, I felt it necessary to introduce the "make" tool.
  In particular, creating the necessary Docker image is slow, and I didn't
  want to have to repeat that except when truly necessary.

  That, in turn, means there are now many more configuration files, as
  well as auxiliary files created by the Makefile. The directory tree was
  becoming hopelessly cluttered. To keep things straight in my head, I felt
  it was really necessary to reorganize the directory structure. The biggest
  change is to put as many of the configuration files as possible in a new
  etc/ directory (the old-school unix name for where to put such things).
  I managed to get almost everything put in there. The one major holdout is
  the tsconfig files; I just couldn't find a way to get TypeScript to run
  without its config files at the top level of the project. Slightly
  annoying, but then, there are so many more annoying things about TypeScript.

  Anyhow, accomplishing the configuration file rearrangement resulted in
  updating eslint. Unfortunately, it went through a _major_ rewrite from
  version 8 to 9, and prettier-eslint has not been updated to work with
  the new version. I tried to work on that update myself, but prettier-eslint
  is incredibly intricate in the way that it handles configurations because
  it is trying to provide a great deal of flexibility and power, and it is
  trying to infer prettier configuration from eslint configuration (and maybe
  even vice-versa as well, I'm not sure). Since we were only using a tiny
  fraction of that power, it turned out to be significantly easier to just
  replace prettier-eslint with a custom script tools/prettiest.js that runs
  first prettier, then eslint. It also meant we could get rid of the
  lint-staged tool, so there is that. (While I was at it, I ran the "depcheck"
  tool and got rid of some other unneeded cruft that had accumulated.)

  But now it all works, and as a side benefit since just about every npm
  script now runs through make, you should never need to worry about
  running install before dev or build before preview, etc. Make keeps track
  of what depends on what and whether/how to redo the prerequisites before
  taking the requested action. Even better, if you just ran successful
  end-to-end tests, which take a while now, then `git commit` will not have
  to re-run them.

  Those are the major points. In addition, there are a number of minor changes
  resulting from errors uncovered in getting all the tests to work, etc:

  - Reordering of element attributes and other reformatting in vue components,
    because with the lint updates and reconfiguration, it now seems
    significantly stricter about vue templates.
  - First pass at an updated User Guide for ui2; it definitely needs more work.
  - Some other more minor documentation updates.
  - Updates tools/editor/autoformat.el so that emacs can use the new
    "prettiest" tool for formatting (even though I know I am likely the only
    one in the world who will ever use that).

  As per Numberscope discussion today, this is the last missing element
  of the end-to-end testing PR. With these skipped tests, we are flagging
  that there are known concerns we want to resolve at least by beta, if not
  alpha. Also fixes a small gap in the docs for running from source that
  Aaron noticed in the meeting.

  With this, the PR will be marked ready for final review.

…zooms

…/pan

…tion