style: autoformat code and add github action to check formatting

[brycedrennan]

Automatic code formatting reduces mental overhead for developers.

• Code style is consistent in this repo and across other repos
• Future diffs will not have anything relating to style changes

Code can be formatted by:

• pip install black isort
• make af (short for autoformat)

A github action that automatically checks code formatting is also added here, ensuring consistent style going forward.

The specific code formatter used here is extremely safe to use (as in it doesn't break code), very fast, and makes smart choices about formatting.