automatically publish AMUSE versions on PyPI from github

[rieder]

It's possible to make a CI workflow that publishes new versions on PyPI automatically. This would be very practical to have implemented. E.g.: check if a build is working correctly, if so, tag it as a new version and it's automatically pushed to PyPI as well. https://packaging.python.org/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/

Need to check how this is done in practice...