Test on RPM-based distribution

[stefan6419846]

At the moment, our tests are only running on Ubuntu 22.04. This does not allow for the full suite of RPM-based tooling/testing, as required for #25. Therefore, a corresponding RPM-based distribution, probably OpenSUSE Leap due to already using it for development, should be added to GitHub Actions.

Docs: https://docs.github.com/en/actions/using-jobs/running-jobs-in-a-container, containers are at https://hub.docker.com/r/opensuse/leap/tags

It seems like we need at least OpenSUSE Leap 15.2 for https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/), but as the currently supported minimum version is 15.5 anyway, this should be no big deal.