feature: Git files should support viewing everything as if you were at the root of the repo

[WolfeCub]

Did you check the docs?

• I have read all the snacks.nvim docs

Is your feature request related to a problem? Please describe.

In telescope and fzf-lua git_files would show you all the files from the root of the repo. However in snacks it's relative to your current working directory.

Describe the solution you'd like

Add another function, option or change the behaviour of git_files so that there's a way to view the directory contents as if you were at the root from any sub-directory. The files should be formatted relative to the repo root regardless of where in the repo you are.

Describe alternatives you've considered

I would write it myself but the documentation around cwd and transform to get the correct formatting is unclear.

Additional context

No response