Instead of using a subtitle, move the stability warning into an information popover. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3051>
There aren't many shortcuts and all of them are standard, but documenting them is still good practice, and our main menu is a tad bit less empty. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3051>
Now that we switched to AdwApplication, we can automate loading the custom stylesheet by simply using the expected name and resource prefix. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1997>