[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/RequiresItemBehavior.cs

@@ -0,0 +1,33 @@
+using UnityEngine;
+
+[RequireComponent(typeof(Interactable))]
+public class RequiresItemBehavior : InteractionRequirementBase
+{
+    [Header("Required Item")]
+    public PickupItemData requiredItem;
+
+    public override bool TryInteract(FollowerController follower)
+    {
+        var heldItem = follower.currentlyHeldItem;
+        if (heldItem == requiredItem)
+        {
+            OnSuccess?.Invoke();
+            return true;
+        }
+        else
+        {
+            string requiredName = requiredItem != null ? requiredItem.itemName : "required item";
+            if (heldItem == null)
+            {
+                DebugUIMessage.Show($"You need {requiredName} to interact.");
+            }
+            else
+            {
+                string heldName = heldItem.itemName ?? "an item";
+                DebugUIMessage.Show($"You need {requiredName}, but you are holding {heldName}.");
+            }
+            OnFailure?.Invoke();
+            return false;
+        }
+    }
+}