Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibGUI/GDesktop.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/Badge.h>
+#include <AK/Function.h>
+#include <SharedGraphics/Rect.h>
+
+class GEventLoop;
+
+class GDesktop {
+public:
+    static GDesktop& the();
+    GDesktop();
+
+    String wallpaper() const;
+    bool set_wallpaper(const StringView& path);
+
+    Rect rect() const { return m_rect; }
+    void did_receive_screen_rect(Badge<GEventLoop>, const Rect&);
+
+    Function<void(const Rect&)> on_rect_change;
+
+private:
+    Rect m_rect;
+};