Replacement for `pkg_resources`

[jbylund]

pkg_resources is now deprecated in favor of importlib.metadata / importlib_metadata (source). Right now it causes warnings and in the future (3.12?) I think it will stop working entirely. I saw there was a related pr but it was using importlib.metadata which apparently has different behaviors on some versions of python and caused issues for some users (ref). Maybe it would be acceptable to use importlib_metadata (the backport) either on all versions of python or only when necessary.

[apetenchea]

Fixed in #250