Run pre-commit in GitHub Actions

[jonafato]

As a followup to #52, we should run these tasks in GitHub Actions. Generally speaking,

• Autoformatters should commit changes back to pull requests
• Linters, etc. should fail with an error like any other test step

[kjaymiller]

Not sure this is possible (or at least will be supported long term) - https://github.com/pre-commit/action has been deprecated in favor of running their own CI

[jonafato]

It's possible, I've done it on tons of repositories. We don't need the official action for it. Self-assigned, so I'll follow up with a PR.

[jonafato]

This is half-addressed by #77. Autoformatters committing back to be addressed in another change.