windowManager: Add shortcut for toggling quick settings

Ever since the various status menus were combined into a single
aggregate menu, the menu has been an important entry point. Alas,
we never got around to adding a shortcut for it, not least because
there never was a good candidate.

We just freed super+s which works as either "system" or
"(quick) settings", so use that.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/5670

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2716>

data/50-gnome-shell-system.xml

@@ -8,6 +8,9 @@
 	<KeyListEntry name="toggle-message-tray"
                       description="Show the notification list"/>
 
+	<KeyListEntry name="toggle-quick-settings"
+                      description="Open the quick settings menu"/>
+
 	<KeyListEntry name="focus-active-notification"
                       description="Focus the active notification"/>
 

data/org.gnome.shell.gschema.xml.in

@@ -183,6 +183,13 @@
         Keybinding to toggle the visibility of the notification list.
       </description>
     </key>
+    <key name="toggle-quick-settings" type="as">
+      <default>["&lt;Super&gt;s"]</default>
+      <summary>Keybinding to toggle the quick settings menu</summary>
+      <description>
+        Keybinding to toggle the quick settings menu.
+      </description>
+    </key>
     <key name="focus-active-notification" type="as">
       <default>["&lt;Super&gt;n"]</default>
       <summary>Keybinding to focus the active notification</summary>