Add script for generating constraints for all supported Python versions

[redeboer]

It should be possible to generate constraint files for all Python versions in a oneliner or script, using Conda. For instance:

supported_versions=(3.7 3.8 3.9 3.10 3.11)
for version in ${supported_versions[@]}; do
  conda create -n py${version} "python==${version}.*" --force -y
  conda activate py${version}
  pip install git+https://github.com/ComPWA/update-pip-constraints@main
  update-pip-constraints
done

In addition, supported_versions could be determined from setup.cfg, as happens in ComPWA/actions/create-python-version-matrix@v1.