Added protected OnEvent functions for inheritance

SDLU_Example/header.hpp

@@ -1,2 +1,30 @@
 #pragma once
-#include "SDLU.hpp"
+#include "SDLU.hpp"
+#include <iostream>
+
+class MyWindow :
+    public sdlu::RenderWindow
+{
+public:
+    MyWindow(Uint32 width, Uint32 height, const char* title) :
+        RenderWindow(sdlu::Vector2u(width, height), title, NULL, NULL)
+    {
+        // Empty
+    }
+};
+
+void sdlu::RenderWindow::OnCreate()
+{
+    std::cout << "Window was Created!" << std::endl;
+}
+
+bool sdlu::RenderWindow::OnResize()
+{
+    std::cout << "Window was Resized!" << std::endl;
+    return false;
+}
+
+void sdlu::RenderWindow::OnClose()
+{
+    std::cout << "Window was Closed!" << std::endl;
+}