pkg_resources is deprecated

[nhairs]

When running my own tests the following warning is thrown:
/code/.tox/py311/lib/python3.11/site-packages/imageio_ffmpeg/_utils.py:7: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html

The fix appears to be to use importlib.resources

[almarklein]

There's a nice migration guide here: https://importlib-resources.readthedocs.io/en/latest/migration.html

I recently made a similar change in another project (https://github.com/pygfx/wgpu-py/pull/421/files). I expect we can do something similar here.

There's no rush, since its only a warning (for now), but if someone is willing to contribute a PR that'd be great 😊

[almarklein]

Fixed by #109