title: Observe current contentOffset during UiTableView's delete rows animation
body: <p>I set up UI behavior based on tableView's content offset. It works fine and smoothly in all cases excepting one: when tableView starts deleting rows with animation.</p>
  
  <p>The problem appears when before deleting there was a lot of content and a user scrolled a part of it, but after deleting tableView can show the whole content without scrolling. In that case table view changes content offset smoothly and simultaneously with deleting animation. </p>
  
  <p>The main reason causing my problem is scrollView delegate's method <code>scrollViewDidScroll</code> is not invoked during deleting animation and my behavior doesn't work.</p>
  
  <p>I tried to use KVO for observing offset changes:</p>
  
  <pre><code>observation = tableView.observe(\.contentOffset, options: [.new, .old]) { (_, change) in
      print(change)
  }
  </code></pre>
  
  <p>It works better, but fires only once at the first moment with final value so I don't receive any intermediate values which I need for making smooth UI reaction.</p>
  
  <p>Ok, I tried to animate my behavior using <code>UIView.animate</code> and siblings. But found it's difficult to choose parameters to synchronize my animations and tableview's offset animation.</p>
  
  <p>So, what I missed? Is it possible to observe any intermediate offset values during rows deletion animation?  </p>