LibGUI: Desktop, add methods for set background color and wallpaper mode

Libraries/LibGUI/Desktop.cpp

@@ -54,6 +54,16 @@ void Desktop::did_receive_screen_rect(Badge<WindowServerConnection>, const Gfx::
         on_rect_change(rect);
 }
 
+void Desktop::set_background_color(const StringView& background_color)
+{
+    WindowServerConnection::the().post_message(Messages::WindowServer::SetBackgroundColor(background_color));
+}
+
+void Desktop::set_wallpaper_mode(const StringView& mode)
+{
+    WindowServerConnection::the().post_message(Messages::WindowServer::SetWallpaperMode(mode));
+}
+
 bool Desktop::set_wallpaper(const StringView& path)
 {
     WindowServerConnection::the().post_message(Messages::WindowServer::AsyncSetWallpaper(path));

Libraries/LibGUI/Desktop.h

@@ -38,6 +38,10 @@ public:
     static Desktop& the();
     Desktop();
 
+    void set_background_color(const StringView& background_color);
+
+    void set_wallpaper_mode(const StringView& mode);
+
     String wallpaper() const;
     bool set_wallpaper(const StringView& path);