#222: add pipeline for publishing pypi package

[cwschilly]

Fixes #222

wip: pending addition of PyPi token to Pressio's organization secrets

[cwschilly]

@eparish1 @fnrizzi There is already a pip package called ROMtools (link), so we'll have to rename our package.

Any ideas? We could do pressio-romtools, which would be imported with:

import pressioromtools