title: How to avoid scroll jump during loading new items to list?
body: <p>I am developing a chat and now I am dealing with the functionality of loading old messages.
  When the user has scrolled to the beginning, I request a new block of messages and insert it at the top of the list, then calculate how much space this new block took up and scroll down by this value.
  And during this process, you can notice a short jump of the scroll. How can it be avoided?</p>
  <p><a href="https://www.youtube.com/watch?v=LBcGkjgnazk&amp;feature=youtu.be&amp;ab_channel=EugeneDerevyanko" rel="nofollow noreferrer">demo is here</a></p>