FEAT: set preferred Python version for dev environment

[redeboer]

It is now possible to specify which Python version you want to use in your developer environment by specifying the --dev-python-version argument for the check-dev-files hook. For example:

  - repo: https://github.com/ComPWA/repo-maintenance
    rev: 0.1.8
    hooks:
      - id: check-dev-files
        args:
          - --dev-python-version=3.11  # your preferred version
          - --repo-name=ampform
          - --repo-title=AmpForm

This updates (if avaiable) the Conda environment, the GitHub workflows, the RTD config, and the GitPod config.