Add publication to PyPI as github workflow

Automatic publication to PyPI via a pushed tag or via a Release on Github is straitforward.  It should be added to the template.

See https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/ and my own example at https://github.com/mpi-astronomy/snowblind/blob/main/.github/workflows/publish.yml