title: How to handle "Done" return key press event in rxSwift?
body: <p>While exploring <a href="https://github.com/ReactiveX/RxSwift" rel="noreferrer">RxSwift</a></p>
  
  <p>I found just <code>textField.rx_text.asObservable()</code> property, that fires event every keyboard button is hit. </p>
  
  <p>But how do we handle "search" or "done" button press events? I'd like to fire search only after these actions, not "search as you type".</p>