We've provided the code for a basic list of items. Now it's your turn to extend it. Do your work in app/application.rb.

In applications built on Rack, we use the noun "route" to refer to a path that the application has a special response to.

So, for example, if we navigated to a /shoes route, we would expect the application to show us information about shoes. A /profile route might show information about a user who's logged in to an application. Finally, a /logout route might update some information to let the server know the user is no longer logged in.

1. Create a new class array called @@cart to hold any items in your cart.
2. Create a new route called /cart to show the items in your cart.
3. Create a new route called /add that takes in a GET param with the key item. This should check to see if that item is in @@items and add it to the cart if it is. Otherwise it should give an error.