Introduce pre commit

[schuellerf]

Trigger was #133 where Schutzfile had a typo and it took a while to find it

[schuellerf]

To test, this should be sufficient:

pip install pre-commit
pre-commit install  # this is global

then mess with Schutzfile and try to commit locally

[schuellerf]

btw. we can also integrate this check in github like so:
https://github.com/osbuild/.github/blob/main/.github/workflows/pre-commit.yml#L20
(preferably with an up to date version :-D )

[thozza]

The change looks OK. I'm wondering if it would make sense to run tests, which are performed by the pre-commit config but missing in GH actions, as part of PRs?

Mostly to prevent introducing new issues and makinbg life of anyone using the pre-commit hooks harder.