Can't be installed with pipx

[micahsnyder]

It seems if you install Mussels with pipx, then it will fail with this error when you run it (at least in github's macos runner. Seemed to work okay in their ubuntu runner:

Traceback (most recent call last):
  File "/Users/runner/.local/bin/msl", line [5](https://github.com/Cisco-Talos/clamav-mussels-cookbook/actions/runs/10647162151/job/29514803498?pr=63#step:6:6), in <module>
    from mussels.__main__ import cli
  File "/Users/runner/.local/pipx/venvs/mussels/lib/python3.12/site-packages/mussels/__main__.py", line 42, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'

See also:
https://stackoverflow.com/questions/60032087/why-my-package-cant-be-installed-with-pipx

[micahsnyder]

It's possible we just need to set setuptools as a dependency