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/GStatusBar.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class GLabel;
+class GResizeCorner;
+
+class GStatusBar : public GWidget {
+public:
+    explicit GStatusBar(GWidget* parent);
+    virtual ~GStatusBar() override;
+
+    String text() const;
+    void set_text(const StringView&);
+
+    virtual const char* class_name() const override { return "GStatusBar"; }
+
+private:
+    virtual void paint_event(GPaintEvent&) override;
+
+    GLabel* m_label { nullptr };
+    GResizeCorner* m_corner { nullptr };
+};