title: Angular 7 cdk-virtual-scroll-viewport - virtual scroll
body: <p>Is there any event available with, cdk-virtual-scroll-viewport to find the element in the list is rendered or not. 
  for example while scrolling through a list of  like below, is there a way to identify a particular li is rendered or not or a  set of new elements are rendered into the DOM. </p>
  
  <ul>
  <li>item</li>
  <li>item</li>
  <li>item</li>
  </ul>