change keyboard demo to event listener

c_os/user/demo/KeyboardDemo.h

@@ -13,14 +13,18 @@
 
 #include "kernel/Globals.h"
 #include "kernel/threads/Thread.h"
+#include "user/KeyEventListener.h"
 
 class KeyboardDemo : public Thread {
 private:
     KeyboardDemo(const KeyboardDemo& copy) = delete;
 
+    KeyEventListener listener;
+
 public:
-    KeyboardDemo() {
+    KeyboardDemo() : listener(*this) {
         kout << "Initialized KeyboardDemo" << endl;
+        kevman.subscribe(listener);
     }
 
     void run() override;