title: Sticky header/item in recyclerview
body: <p>I have successfully implemented sections in a recycler view as shown in the screenshot with two different types of views.
  How do i implement a sticky header in the recycler view.
  I want the 'A' to stick to the top until the user scrolls upwards in which case the next item to stick to the top would be 'B'.
  How do i do this?</p>
  
  <p><a href="https://i.stack.imgur.com/wt9ry.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wt9ry.png" alt="Recycler View"></a></p>