add demo directory

demo/src/demo.cpp

@@ -0,0 +1,21 @@
+/*
+# ______       ____   ___
+#   |     \/   ____| |___|
+#   |     |   |   \  |   |
+#-----------------------------------------------------------------------
+# Copyright 2020, tyra - https://github.com/h4570/tyra
+# Licenced under Apache License 2.0
+# Sandro Sobczyński <sandro.sobczynski@gmail.com>
+*/
+
+#include "demo.hpp"
+
+namespace Tyra {
+
+Demo::Demo(Engine* t_engine) { engine = t_engine; }
+Demo::~Demo() {}
+
+void Demo::init() { TYRA_LOG("Init!"); }
+void Demo::loop() {}
+
+}  // namespace Tyra