message: Adds global difficulty strings
diff: @@ -182,6 +182,12 @@ namespace constants
  const std::string MAIN_MENU_HELP = "Help";
  const std::string MAIN_MENU_QUIT = "Quit";
  + const std::string DIFFICULTY_TITLE = "Difficulty";
  + const std::string DIFFICULTY_BEGINNER = "Beginner";
  + const std::string DIFFICULTY_EASY = "Easy";
  + const std::string DIFFICULTY_MEDIUM = "Medium";
  + const std::string DIFFICULTY_HARD = "Hard";
  +
  const std::string WINDOW_FACTORY_PRODUCTION = "Factory Production";
  const std::string WINDOW_GAME_OVER = "Game Over";
  const std::string WINDOW_MINE_OPERATIONS = "Mine Facility Operations";
  