[Player][Interaction][Assets] Add placeholder assets for some more sprites. Move all to External/Placeholder. Add list of assets with attributions. Pulver combines items now

Assets/Scripts/GameSettings.cs

@@ -28,6 +28,16 @@ public class GameSettings : ScriptableObject
     [Header("Default Prefabs")]
     public GameObject basePickupPrefab;
 
+    [System.Serializable]
+    public class CombinationRule {
+        public PickupItemData itemA;
+        public PickupItemData itemB;
+        public PickupItemData result;
+    }
+
+    [Header("Combination Rules")]
+    public System.Collections.Generic.List<CombinationRule> combinationRules;
+
     // Singleton pattern
     private static GameSettings _instance;
     public static GameSettings Instance {