Add a pre-commit hook to verify license headers

[omad]

We use pre-commit to check for trivial errors in code before committing it. It's useful for keeping formatting consistent and catching errors early that can be picked up with a code linter. Tight feedback loops are better than long ones.

I think it would be worth setting up a pre-commit hook for checking license headers to ensure any files we add or change still include the corrected ODC license.