Add handleMenuType function to ItemRewriter (#3953)

common/src/main/java/com/viaversion/viaversion/rewriter/ItemRewriter.java

@@ -112,7 +112,12 @@ public class ItemRewriter<C extends ClientboundPacketType, S extends Serverbound
             @Override
             public void register() {
                 map(Types.VAR_INT); // Container id
-                handler(wrapper -> {
+                handler(wrapper -> handleMenuType(wrapper));
+            }
+        });
+    }
+
+    public void handleMenuType(final PacketWrapper wrapper) {
         final int windowType = wrapper.read(Types.VAR_INT);
         final int mappedId = protocol.getMappingData().getMenuMappings().getNewId(windowType);
         if (mappedId == -1) {
@@ -121,9 +126,6 @@ public class ItemRewriter<C extends ClientboundPacketType, S extends Serverbound
         }
 
         wrapper.write(Types.VAR_INT, mappedId);
-                });
-            }
-        });
     }
 
     public void registerSetSlot(C packetType) {