Check on sample app suggested in the contributing doc

[jerelmiller]

We had some recent feedback that the instructions in the "Wiring a checkout into an application" may be out of date. The sample tutorial may need to be revisited to see if it still works.

At the very least, we may consider suggesting yalc as a helpful tool. Let's take a look at that doc and ensure its up-to-date so contributors can properly setup the client for local development.