Item is no longer JsonSerializable

before anyone starts screaming:

1) it's easy to create your own wrapper that converts items to arrays
2) there is no longer a single standard way to encode items.
3) the way that item serialization now works requires an ItemSerializer, which, barring singleton use, must be dependency-injected. Since there's no way to inject dependencies into jsonSerialize(), this means that its behaviour cannot be customized.

src/inventory/CreativeInventory.php

@@ -41,7 +41,7 @@ final class CreativeInventory{
 
 		foreach($creativeItems as $data){
 			try{
-				$item = Item::jsonDeserialize($data);
+				$item = Item::legacyJsonDeserialize($data);
 			}catch(SavedDataLoadingException){
 				//unknown item
 				continue;