Separate CLI as an extra

[impredicative]

This is not an urgent request for me, but I think the CLI component and requirements of dressup ought to be separated into an extra installable. The CLI and its numerous requirements could then be installable as dressup[cli] but not as dressup.

This should have two benefits:

1. It will eliminate almost all of the third-party package requirements which a non-CLI user doesn't need or want.
2. It could allow at least dressup (but perhaps not dressup[cli]) to support Python 3.11.

For motivation, consider the httpx package. It is a nice package, and it separates httpx[cli].