refactoring: Using const for game symbol constants

src/main/c/GameTic_Tac_Toe/game.c

@@ -4,7 +4,8 @@ char board[3][3] = {{'1', '2', '3'},
                     {'4', '5', '6'},
                     {'7', '8', '9'}};
 char currentPlayer = 'X';
-
+const char PLAYER_X = 'X';
+const char PLAYER_O = 'O';
 // Funktionen zur Anzeige des Spielbretts
 void displayBoard() {
     printf("Tic-Tac-Toe\n");