feat: add example splash item for inventory testing

scenes/kq4_003_fountain_pool/kq4_003_fountain_pool.gd

@@ -1,6 +1,16 @@
 extends Scene
 
 
+func _ready() -> void:
+	super._ready()
+	var def = ItemDefinition.new()
+	def.id = "splash"
+	def.name = "Splash"
+	def.combination_category = "potion"
+	InventoryManager.register_item_definition(def)
+	give_item("splash")
+
+
 func _on_meadow_interacted() -> void:
 	$kq4_002_meadow.default_script(self)