Here's the JSfiddle for that demo:

https://jsfiddle.net/cbjzped2/

The problem with that is that the grid rows are determined dynamically:

    .item.v2 {
      grid-row: span 2;
    }
    .item.v3 {
      grid-row: span 3;
    }
    .item.v4 {
      grid-row: span 4;
    }
    .item.h2 {
      grid-column: span 2;
    }

I'd much rather drop in a library like MagicGrid or Masonry and deal with it from there, to be honest, instead of trying to hack grid to do it. I think grid could be extended to handle this kind of design but until it is...