Add aria attributes to cart container

[spencercanner]

• Add a role=dialog and aria-modal="true" to the cart container to signify that it's a modal
• Add aria-labelledby to the container, and connect it to the cart header
  • This involved creating a new method of assigning unique cart ids since the time-based approach resulted in the dom updating every time render was called on the cart
  • The new method adds an index property to the cart class and assigns a value based on the order of cart creation (i.e. if there are 3 carts, the indexes of the components will be 0,1,2)
  • The new index property was also used for the cart note id, instead of the time-based id

To 🎩 :

• Navigate a virtual cursor to the cart toggle
• Open the cart by pressing enter on the dialog
• Verify that the cart is announced as a dialog labelled by the cart title
  • The screen reader should announce the cart title (Cart), followed by dialog or web dialog

Browsers:

• Safari - Mac - VoiceOver
• Firefox - Windows - NVDA