Actions: Style Checker and Rspec

[mattzollinhofer]

• use https://github.com/testdouble/standard

[tannerwernecke]

Adding this style checker to Github to run automatically with a PR seems to be non-trivial. I can definitely go about doing it if it would be worthwhile, but if not, I have standardrb and can use it locally to check before each PR.

Here is what seems to be the best walkthrough for going about adding it to Github: https://developer.github.com/apps/quickstart-guides/creating-ci-tests-with-the-checks-api/