workspace-indicator: Set title and icon on prefs page

The window-list extension will add the workspace prefs as
additional page, so it needs a title and icon for the
view switcher.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/344>

extensions/workspace-indicator/workspacePrefs.js

@@ -222,7 +222,10 @@ export class WorkspacesPage extends Adw.PreferencesPage {
     }
 
     constructor(settings) {
-        super();
+        super({
+            title: _('Workspaces'),
+            icon_name: 'view-grid-symbolic',
+        });
 
         this.add(new GeneralGroup(settings));
         this.add(new WorkspacesGroup());