add forward declaration examples

add class & inheritance examples

CPlusPlus/Classes/Monster.cpp

@@ -0,0 +1,18 @@
+#include "Monster.h"
+
+Monster::Monster(int strength) : Entity("My Monster"), _strength(strength)
+{
+	this->name = "My Monster";
+}
+
+std::string Monster::ToString()
+{
+	return name + " " + "(" + std::to_string(_strength) + ")";
+	// TODO: show format
+}
+
+int Monster::Compare(ICompareable* other)
+{
+	// TODO: implement later
+	return 0;
+}