LibGUI: Let Desktop:the() manage SystemEffects inside LibGUI

These settings might well ultimately be factored into a dedicated
settings manager, but until then, a charitable interpretation of
Desktop::the() as the desktop environment will suffice.

Userland/Libraries/LibGUI/Desktop.h

@@ -10,6 +10,7 @@
 #include <AK/Function.h>
 #include <AK/String.h>
 #include <LibGUI/Forward.h>
+#include <LibGUI/SystemEffects.h>
 #include <LibGfx/Rect.h>
 #include <Services/Taskbar/TaskbarWindow.h>
 #include <Services/WindowServer/ScreenLayout.h>
@@ -34,6 +35,9 @@ public:
     RefPtr<Gfx::Bitmap> wallpaper_bitmap() const;
     bool set_wallpaper(RefPtr<Gfx::Bitmap> wallpaper_bitmap, Optional<String> path);
 
+    void set_system_effects(Vector<bool> effects) { m_system_effects = { effects }; };
+    SystemEffects const& system_effects() const { return m_system_effects; }
+
     Gfx::IntRect rect() const { return m_bounding_rect; }
     Vector<Gfx::IntRect, 4> const& rects() const { return m_rects; }
     size_t main_screen_index() const { return m_main_screen_index; }
@@ -59,6 +63,7 @@ private:
     unsigned m_workspace_columns { 1 };
     Vector<Function<void(Desktop&)>> m_receive_rects_callbacks;
     bool m_is_setting_desktop_wallpaper { false };
+    SystemEffects m_system_effects;
 };
 
 }