Update continuous integration

[marcosfelt]

Problem: Publishing this project to pypi was manual, meaning I rarely published updates.

Solution: This changes to a new GH action for publishing to pypi automatically based on version increments in pyproject.toml. It also adds a build step so that tests and publishing work off the same build. Other changes:

• Matrix testing across windows, mac and ubuntu and multiple python versions
• Inlined units test into package to enable running them from the installed package (just run summit-tests)
• Updated packages to fix Numpy issue in strategies #172
• Fixed issue with readthedocs not working due to Jinja 2 imports have been deprecated sphinx-doc/sphinx#10291

[marcosfelt]

Closed in favor of #174, #175, #176, #177