DisplayProperties: Add a menubar

Add a menubar to the `DisplayProperties` application to make it
more consistent with the other programs in the system.

Applications/DisplayProperties/main.cpp

@@ -1,7 +1,11 @@
 #include "DisplayProperties.h"
 #include <LibDraw/PNGLoader.h>
+#include <LibGUI/GAboutDialog.h>
+#include <LibGUI/GAction.h>
 #include <LibGUI/GApplication.h>
 #include <LibGUI/GBoxLayout.h>
+#include <LibGUI/GMenu.h>
+#include <LibGUI/GMenuBar.h>
 #include <LibGUI/GWidget.h>
 #include <LibGUI/GWindow.h>
 
@@ -12,12 +16,28 @@ int main(int argc, char** argv)
 
     auto window = GWindow::construct();
     window->set_title("Display Properties");
-    window->move_to(100,100);
+    window->move_to(100, 100);
     window->resize(400, 448);
     window->set_resizable(false);
     window->set_main_widget(instance.root_widget());
     window->set_icon(load_png("/res/icons/16x16/app-display-properties.png"));
 
+    // Let's create the menubar first
+    auto menubar = make<GMenuBar>();
+
+    auto app_menu = GMenu::construct("Display Properties");
+    app_menu->add_action(GCommonActions::make_quit_action([&](const GAction&) {
+        app.quit();
+    }));
+    menubar->add_menu(move(app_menu));
+
+    auto help_menu = GMenu::construct("Help");
+    help_menu->add_action(GAction::create("About", [&](const GAction&) {
+        GAboutDialog::show("Display Properties", load_png("/res/icons/32x32/app-display-properties.png"), window);
+    }));
+    menubar->add_menu(move(help_menu));
+
+    app.set_menubar(move(menubar));
     window->show();
     return app.exec();
 }