title: Compositional layout with centred items and centred paging
body: <p>Need some help here. I'm building an interesting layout, where cells are centered depending on their count. Probably, best thing to explain is to illustrate a little demo.
  Here it is:</p>
  <p><a href="https://i.stack.imgur.com/o0tto.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o0tto.png" alt="enter image description here" /></a></p>
  <p>On the left we have a behaviour of how layout acts depending on items in datasource. On the right - illustration of seven cells in collection view.</p>
  <p>I have some thoughts about triple grouping, but probably you can help me with more simple solution using compositional layout.</p>
  <p>Thanks!</p>