Flit & pypi

[fanoway]

I've set this up using flit and pyproject.toml so it can be published to pypi inline with PEP517.

I tested this using the test.pypi site and it all seemed to work.

I also added a github action to publish to pypi when a release is done in Github.

Finally requirements are updated to work with flask 2.0

I hope this is helpful

[fanoway]

You'll have to set these two repository secrets for the publish on release pipeline to work

PYPI_USERNAME PYPI_PASSWORD