When a user types or deletes in the
<input />, then that will trigger a change event, which will call
handleUserInput. That's good!
handleUserInput will set
this.state.userInput equal to whatever text is currently in the input field. That's also good!
There's only one problem: you can set
this.state.userInput to whatever you want, but
<input /> won't care. You need to somehow make the
<input />'s text responsive to
Easy enough! You can control an
<input />'s text by setting it's