Improve README and CONTRIBUTING guides

[stefannibrasil]

The README now contains steps to generating the code coverage report, how to use the SkunkScore as a refactoring guide, and a separate Contributing guide. I also cleaned up a bit the skunk report to help people focus on what matters. It's my first time opening a Pull Request here, curious to see your thoughts!

I have a couple of questions of things I'd like to add in the README:

• What is a healthy SkunkScore to add as an example for people to compare their current score with?
• Are there any Changelog good practices/guidelines to add in the Contributing guide?

Thanks!

I will abide by the code of conduct.

[bronzdoc]

This looks like a good improvement, thanks so much for this @stefannibrasil!

Just left a few comments

[kindoflew]

hi @stefannibrasil! thanks for contributing!

I can answer at least one of your questions -- relating to CHANGELOG.md stuff.

We use a format based on Keep A Changelog. The important things to note are:

• new additions get added under the main (unreleased) heading
• it should be a link to the PR with the following format:

* [<FEATURE | BUGFIX | CHORE>: Description of changes](github.com/link/to/pr)

As far as a good Skunk Score, I'm not really sure, but perhaps @etagwerker could help answer that one?

[codecov]

Codecov Report

Merging #88 (b50c5fd) into main (507a725) will not change coverage.
The diff coverage is n/a.

❗ Current head b50c5fd differs from pull request most recent head cf59df8. Consider uploading reports for the commit cf59df8 to get more accurate results

@@           Coverage Diff           @@
##             main      #88   +/-   ##
=======================================
  Coverage   98.26%   98.26%           
=======================================
  Files          25       25           
  Lines         462      462           
=======================================
  Hits          454      454           
  Misses          8        8           

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[stefannibrasil]

@kindoflew @bronzdoc thank you for your review! I added more details about the Changelog.

@etagwerker do you have any thoughts on adding a "healthy" SkunkScore to add as an example for people to compare their current score with?

[kindoflew]

ping @etagwerker

[etagwerker]

@kindoflew @stefannibrasil At this point I don't have an answer for that... I created an issue to improve this area of the gem: #95

I've been slowly uploading scores to http://skunk.fastruby.io to get a sense of "healthy" skunk scores in real projects. But I don't have any conclusive data yet...

[bronzdoc]

We really appreciate your contribution @stefannibrasil! I apologize for the delay, I think this is good to go and we can improve it later when we tackle #95