マネージャでの背景設定に対応

popcorn/Assets/MyGame/Scenes/MiniGame/Scripts/BGManager.cs

@@ -62,5 +62,13 @@ namespace MyGame.Scenes.MiniGame.Scripts
                 bg.GetComponent<BackGround>()?.SetFence(nextFenceXPos);
             }
         }
+
+        public void SetSky(ScrollGameDifficulty difficulty)
+        {
+            foreach (var bg in bgArray)
+            {
+                bg.GetComponent<BackGround>()?.SetSky(difficulty);
+            }
+        }
     }
 }