Add a style checking script to CI

It's tough to have PRs bounce or to have a back and forth with contributors
about minor style quibbles. Sometimes it ends up just being easier to fix style
after the fact, but let's add some automation to help this!

This commit adds a script to run on CI and locally to verify the style of this
repository. There's a few stylistic guidelines to ensure that definitions are
understandable across the jungle of modules. This consistency should help assist
readability for any future readers!