Add fedora:rawhide to testing matrix
Add a rawhide test (F39) in order to test against Python 3.12.
Currently, the Python 3.120b3 available to Fedora 38 doesn't ship with a setuptools new enough, and so that test fails before tox can even run for the py312 test.
The rawhide test gets much further, but still has failing pylint and flake8 tests -- no big deal, those are problems with those linting frameworks and don't have anything to do with our actual ability to support Python 3.12.
After this MR, I intend to send a separate MR to tag and publish v0.0.3. --js