Fix: favicons command has no attribute cli.

[arielvb]

Hi, Matt,

Thank you for the package.

This pull request is to fix a bug when executing the favicons command. It's just a minor change in pyproject.toml.

The bug occurs with the package published on PyPI:

favicons                       
Traceback (most recent call last):
  File "[edited]/favicons/env/bin/favicons", line 8, in <module>
    sys.exit(cli())
TypeError: 'module' object is not callable

And also with the master branch:

pip install .
poetry run favicons
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: module 'favicons' has no attribute 'cli'

It will be great if you can merge it and publish a new version on PyPI!