Add workflow for automatic publication on PyPI.

[aznashwan]

Although we currently recommend everyone pulls/installs the python-coriolisclient from source, it would be nice to define an automatic workflow for building/publishing a wheel to our PyPI listing:

https://pypi.org/project/python-coriolisclient/

Publishing a version after each PR merge may be a bit overkill and lead to versioning confusion for users, but we should at least aim to have a workflow which publishes the stable/XYZ releases at least.