WindowServer: Start implementing a menu system.

I'm going with a global top-of-the-screen menu instead of per-window menus.
The basic idea is that menus will live in the WindowServer and clients can
create menus via WindowServer requests.

WindowServer/WSMenuItem.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <SharedGraphics/Rect.h>
+
+class WSMenuItem {
+public:
+    enum Type {
+        None,
+        Text,
+        Separator,
+    };
+
+    explicit WSMenuItem(const String& text);
+    explicit WSMenuItem(Type);
+    ~WSMenuItem();
+
+    Type type() const { return m_type; }
+    bool enabled() const { return m_enabled; }
+
+    String text() const { return m_text; }
+
+    void set_rect(const Rect& rect) { m_rect = rect; }
+    Rect rect() const { return m_rect; }
+
+private:
+    Type m_type { None };
+    bool m_enabled { true };
+    String m_text;
+    Rect m_rect;
+};
+