feat(item): add cost attribute and getter function

src/item.py

@@ -11,6 +11,7 @@ class Item:
         self.x = x
         self.y = y
         self.item_type = item_type
+        self.cost = random.randint(5, 10)
 
         # collision rect for player (2 times item size for width and height)
         self.rect = pygame.Rect(self.x, self.y, ITEM_SIZE, ITEM_SIZE)
@@ -50,6 +51,9 @@ class Item:
             pygame.draw.rect(screen, color, draw_rect)
             pygame.draw.rect(screen, COLOR_HP_BAR_BG, draw_rect, 2)
 
+    def get_cost(self):
+        return self.cost
+
 
 # try 50 times to find a free position to spawn item
 def _random_position(room_rect, blocked_rects):