Create PyPI release workflow

[Noordsestern]

For historical reasons, releases are made locally. Add the github-release workflow for pypi. Check BUILD.rst for current approach for releases.
Goals are:

• easier release process

• unified release process

• limit rights on pypi organization

• SSHLibrary pre-releases are published automatically when creating a Github release

• SSHLibrary release are published automaticall when creating a Github release

• SSHLibrary release can be published on test-pypi

• Pypi Token is added to Github secrets with most restrictive permissions