Move theme commands to a top-level Theme menu

extensions/modula2-workbench/src/browser/modula2-workbench-frontend-module.ts

@@ -26,8 +26,10 @@ class MenusContribution implements MenuContribution {
     const submenu = ['menubar', 'modula2'];
     menus.registerSubmenu(submenu, 'Modula-2');
     menus.registerMenuAction(submenu, { commandId: Commands.about.id });
-    menus.registerMenuAction(submenu, { commandId: SwitchThemeCommand.id });
-    menus.registerMenuAction(submenu, { commandId: ToggleThemeCommand.id });
+    const themeMenu = ['menubar', 'theme'];
+    menus.registerSubmenu(themeMenu, 'Theme');
+    menus.registerMenuAction(themeMenu, { commandId: SwitchThemeCommand.id });
+    menus.registerMenuAction(themeMenu, { commandId: ToggleThemeCommand.id });
   }
 }