Merge pull request #936 from ethanwhite/publication-release

Update to newest pa11y and dependencies

Incorporate Virnaliz's edits on learning theories

Co-authored-by: Virnaliz Cruz  <virnaliz.cruz@weecology.org>

Make schedule accessible to screen readers

Drop confusing connection between shrub volume exercises

Shrub Volume Data Basics & Shrub Volume Data Frame use different data sources so
linking them was confusing.

Fixes #761.

Merge pull request #728 from ethanwhite/knitr-update

Rework knitr demo for smoother flow

Merge pull request #613 from brymz/bad-links

fix or remove broken links