title: Increase UINavigationBar title font size on scroll
body: <p>I saw this effect today where the navigation bar title seemingly starts within the view, then shrinks and moves upwards into the navigation bar's title as you scroll the page, it then reverses to its original state when scrolled back to the top.</p>
  
  <p><img src="https://i.stack.imgur.com/cB4pt.jpg" alt="SoulCycle initial view">
  <img src="https://i.stack.imgur.com/Lj6nv.jpg" alt="SoulCycle intermediate view">
  <img src="https://i.stack.imgur.com/Z9WaU.jpg" alt="SoulCycle final view"></p>
  
  <p>Does anyone have any insight on how this is done? Is a navigation bar used at all, or is it being mocked using a UIView that shrinks in height and the background colour darkens? Perhaps the title is a label converted to a UIImage and scaled down rather than the font size decreasing?</p>
  
  <p>Just speculating on possible techniques. </p>
  
  <p>Would love to get some opinions on this. Thanks in advance.</p>