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/GCheckBox.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/Function.h>
+#include <LibGUI/GAbstractButton.h>
+
+class GCheckBox : public GAbstractButton {
+public:
+    GCheckBox(const StringView&, GWidget* parent);
+    explicit GCheckBox(GWidget* parent);
+    virtual ~GCheckBox() override;
+
+    virtual void click() override;
+
+    virtual const char* class_name() const override { return "GCheckBox"; }
+
+private:
+    virtual void paint_event(GPaintEvent&) override;
+};