chore: add pre-commit workflow to ci for license checks

[amoeba]

Follow-on to #73.

Adds a new GHA workflow to run pre-commit and a pre-commit config that runs https://github.com/amoeba/license-header-check/. Includes fixes to files that were missing licenses.

[amoeba]

As a follow-on, we could:

1. Add more pre-commit checks that make sense
2. Gate our main workflows on the pre-commit workflow if others like that

[amoeba]

Rebased the pr and updated the workflow. The pre-commit only checks to make sure we spell our name right at the moment. I did this assuming Apache RAT can check that the entire license is right. cc @zeroshade