Add github action to automate creating PyPI packages

[flacjacket]

Add a new github action that will build and upload PyPI packages when new releases are cut. This works by running but not uploading the package when a tag is created, then, when the Github release is published, the build is run and the package is pushed to PyPI.

To work, this will also require a PyPI API token. I am able to generate a token, but do not have access to add it as a Github Actions secret to this repo.