add carton editor for mix carton

lib/domain/constants.dart

@@ -95,6 +95,11 @@ const carton_from_shipments = "From shipments";
 const carton_small_bag = "Small bag";
 const carton_mix_box = "Mix box";
 
+// carton Size
+const standardCarton = "Standard carton size";
+const customCarton = "Custom size";
+const packageCartion = "Package";
+
 //Mix types
 const mix_delivery = "Mix Delivery";
 const mix_pickup = "Mix Pickup";