Add no-commit-to-branch to pre-commit-config.yaml

[samjmolyneux]

If we are only using pull requests, might make sense to enable

  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v6.0.0
      - id: no-commit-to-branch
        args: ["--branch", "main"]

to prevent any "oops, I'm on main" moments.