Add pre-commit hooks
This ensures a few things are correct before we commit and/or push, making life a bit easier for both our contributors and our maintainers since some things should no longer end up in the MRs.
Activate via: $ pre-commit install $ pre-commit install --hook-type pre-push
The latter is required for the ci-templates hooks which are pre-push only.
Could prevent accidents like in !933 (comment 2066577), cc @JoseExposito