Support for Gnome 40

[sluedecke]

• Support for Gnome 40 incl. preferences
• dropped support for older Gnome versions since prefs now use GTK4

[da2x]

Thanks for your contribution. Please see the status update in #61.

[mikoducky]

yo @sluedecke

any ideas on getting settings to work here again? we're now moving ahead onto gnome 42.4, and options no longer show up

[AlexisWilke]

@mikoducky I tried this as well, I'm on 22.04 now and the default version stopped working. So I used the code here to make it work again.

One thing: I edited the version in the list of versions to add "42" and it worked. My gnome shell says I'm in "42.5" but it looks like "42" was sufficient.

Edit metadata.json and change the version:

"shell-version": [
  "3.18", 
  "3.28",
  "42"
],