Add a loading indicator to UI for request in progress using setState()

In this lesson we will add state to our component to indicate whether we are loading to the user. We will "begin loading" before submitting our request to an API and then set "end loading" once the request is complete using Promise.prototype.then and setState(). This gives users a better experience than being left hanging wondering if their action of clicking the button had any effect. Now they will at least have some indication that work is being done while the request is in progress.