This commit removes GitHub workflows and switches to GitLab CI setup. It updates the project description, dependencies, and classifiers for Checkmk 2.3 compatibility. Additionally, it includes the latest version of Versioneer from PyPI.

This change renames the pyproject.toml file to pyproject.toml.bak to indicate a backup version. No other modifications were made to the file contents.

Renamed the setup.py file to setup.py.bak for backup purposes. This change ensures the original file is preserved while making it clear that it is a backup.

Added a step to install versioneer with the `--vendor` flag in the CI pipeline. This ensures versioneer is properly set up for managing versioning during builds. The change helps streamline the build and deployment process.

This change updates the .gitlab-ci.yml file to include versioneer in the pipeline dependencies. It ensures proper version management during the build process. The renaming of `versioneer.py` to `versioneer.py.bak` is likely related to this adjustment.

Introduced a `pyproject.toml` file to define project metadata, dependencies, and Python version requirements. Added a `.gitlab-ci.yml` for automated builds and PyPI package uploads in the CI pipeline.

This reverts commit e5e6e8ae.

- also remove travis config