Add scope completion

[usrme]

This would be nothing more than the ability to Tab-complete the scope value based on the staged changes. For example given the following changes:

$ git status
On branch main
Your branch is up to date with 'origin/main'.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        deleted:    configs/files/nvchad/chadrc.lua
        modified:   configs/files/nvchad/custom/chadrc.lua
        deleted:    configs/files/nvchad/init.lua
        deleted:    configs/files/nvchad/plugins.lua

I would now be able to cycle through the unique path segments that have changed when presented with the scope option:

$ cometary
                                                                                     
  What are you committing? refactor: Changes that neither fix a bug nor add a feature
  What is the scope? (Enter to skip / Esc to cancel) [12/69]:                        
  > ...

For the above set of changes I'd choose configs/files/nvchad as the scope as that represents, to me, the most logical parent to group the changes by meaningfully, so I would just be able to get that filled with just by pressing Tab three times. Once for configs, once for configs/files, and once for configs/files/nvchad.

This also has the tangential benefit of always being able to validate what were the changed files as I sometimes forget to run git status.