Toolchain update
Apparently setuptools went ahead and added support for pyproject.toml
while I wasn't paying attention. The era of duplicating metadata to
setup.cfg is finally over.
Updating TOML parsing for Python 3.11
Use tomllib if available, else use toml.
An upcoming release will drop support for toml and therefore become
supported on Python 3.11+ only.
Toolchain updates to accompany migration away from setup.py
Add license file; fix to makefile
Bug fix for multivariate options
Fix Makefile; pipx no longer supports --spec
Documentation; mypy integration into tests