Add instructions to install gh with Flox #9397

Describe the feature or problem you’d like to solve

I'd like to be able to install gh through Flox, and manage its version together with that of other packages in my development environment.

Proposed solution

flox install gh
This would allow me to add the .flox directory in my git repo, and share it with my colleagues, to ensure we're all using the same version of gh and accompanying packages.