Adding quantity buttons to template

One of the cool features that the completed version of the store has is the ability to increment and decrement the quantity of an item directly from the shopping cart. [demonstrate this].

So let's add this feature to our project now.

In our template, let's add two buttons into the cart item section. The first will have text content of a + and the second will have a -. For styling purposes, we'll give each a class btn.