Ruby Xcodeproj: Add a file to GroupReference in a Workspace

Question

Im looking at https://github.com/CocoaPods/Xcodeproj with the goal of adding some files into the iOS workspace (not project).

Doing so manually will look like the change like this

Here I added manually the folder Package1 (which is a Swift Package) into the group named Packages in the workspace.

BUT I'd like to do it in a Ruby script that uses Xcodeproj gem. Any idea?