Format / lint via pre-commit

[asottile]

No description provided.

[asottile]

Mostly RFC -- pre-commit is a git hooks / linting framework that I maintain. I finally decided to do this after pushing yet another linting error and waiting a half hour for CI to tell me I typo'd a variable name -- realize I lean on the tools too much :)

If any of the formatting is off I'm happy to dial it back, this is using most of the formatting that I usually use myself. I can also add import ordering since that's another one that's commonly back-and-forthed.

let me know what you think @dahlia!

[dahlia]

Looks good to me in general!