added number of cards function

Project 1/Deck.py

@@ -24,4 +24,7 @@ class Deck:
             return None
         card = self._cards[self._next_card]
         self._next_card += 1
-        return card
+        return card
+    
+    def number_of_cards(self) -> int:
+        return len(self._cards) - self._next_card