Add a command to open the file picker in the current directory

[oati]

Describe your feature request

Right now, it seems like the file picker sets its root directory to the git repository of the project.
In large projects, I often want to work only within some subdirectory of the git repo.
So, a command like <space>c for "open file picker in the current directory" might be useful.

[the-mikedavis]

This was actually just merged a few hours ago! #1600

The new binding is spaceF.