Creating a cart app with GetX

We will be reusing the same screens we created in the previous chapters, with some editions specific to GetX. Let's begin by creating our cart application using GetX:

1. Create a new Flutter app named cart_getx and add dependencies for GetX from pub.dev.
2. Copy the item.dart file from the previous chapter's code into the lib folder of your cart_getx app. Make sure to add the dependency for the equatable package from pub.dev.
3. Create a new file named cart_controller.dart and add the following class:

   class Cart {
     List<Item> items = populateItems();
     List<Item> cart = [];
     Cart({required this.cart});
   }

   This is a very simple, self-explanatory class that holds our static item list and an initially empty cart.

   Don't forget to add the following import in order to make the Item class work:

   import 'item.dart';

4. In the same cart_controller.dart file, underneath the Cart class, add the...