add demo directory

demo/inc/demo.hpp

@@ -0,0 +1,30 @@
+/*
+# ______       ____   ___
+#   |     \/   ____| |___|
+#   |     |   |   \  |   |
+#-----------------------------------------------------------------------
+# Copyright 2020 - 2022, tyra - https://github.com/h4570/tyra
+# Licenced under Apache License 2.0
+# Sandro Sobczyński <sandro.sobczynski@gmail.com>
+*/
+
+#pragma once
+
+#include <engine.hpp>
+#include <game.hpp>
+
+namespace Tyra {
+
+class Demo : public Game {
+ public:
+  Demo(Engine* engine);
+  ~Demo();
+
+  void init();
+  void loop();
+
+ private:
+  Engine* engine;
+};
+
+}  // namespace Tyra