Support display: grid-lanes (aka masonry layout) #910
Description
What problem does this solve or what need does it fill?
display: grid-lanes (previously known as "masonry") is a new layout mode which is useful for creating layouts that are otherwise difficult to achieve: https://webkit.org/blog/17660/introducing-css-grid-lanes/
What solution would you like?
Implement https://www.w3.org/TR/css-grid-3/
It may well make sense to implement https://www.w3.org/TR/css-grid-2 (subgrid layout) first.
Additional context
Safari/Webkit now have an implementation of display: grid-lanes, and it feels like the spec is starting to settle.