Test with more Python versions

[eshwen]

In theory, this package should be compatible with Python <=3.9, and >=3.11. But I should test, just in case

Then I can run any CI pipelines with these additional Python versions, extend the Python version range in pyproject.toml, as well as the Python badge in the README to showcase compatibility

With Python >= 3.11, tomli is included in the standard library. So maybe I can put constraints on the dependency to only install for <= 3.10