Clock: Turns the clock window from guitest2 into a separate program.

We can't not have a desktop clock app. :^)

Clock/ClockWidget.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class ClockWidget final : public GWidget {
+public:
+    explicit ClockWidget(GWidget* parent = nullptr);
+    virtual ~ClockWidget() override;
+
+private:
+    virtual void paint_event(GPaintEvent&) override;
+    virtual void timer_event(GTimerEvent&) override;
+
+    time_t m_last_time { 0 };
+};
+