Add CD for pypi and conda

[joshuatorrance]

We need splitnc added to pypi and conda.

I've followed the instruction and copied the workflow from here:
https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/

Will need to do some of the dev work in this PR due to required interactions between github and the package services.

To do:

• Setup workflow to pypi
  • Test with test.pypi
  • Remove test.pypi once all is working
  • Reset version number once all is working (this will leave a mild mess in test.pypi but that's okay)
• Setup workflow to Conda
  • Is there a Conda test environment?

[joshuatorrance]

Closing this PR in favour of #2