Add pre-commit instructions

[oindrillac]

Add steps on how to run pre-commit checks on your code before creating PRs to how to contribute doc or another doc (if there's a better location)

[MichaelClifford]

@oindrillac let's make this its own short doc that that explains installing pre-commit and what the .pre-commit-config.yaml file does, in addition to using it.