Add a --force-listing ooption

[rbanffy]

Description

While investigating #49 and #58, it became evident an option to list (and, therefore, pin the version) of a package that's not in the minimal set of requirements would be useful. The example in question was Django, but the same applies to many other packages that depend on others where you would want to pin the "main" package as well as the minimal set of requirements.

[github-actions]

Stale issue message