[csswg-drafts] [css-grid] Decorative grid-cell pseudo-elements

tabatkins has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-grid] Decorative grid-cell pseudo-elements ==
@jensimmons proposes adding a grid-cell pseudo so you can add 
(responsive) decorative elements to grids without having to add empty 
elements to your page.

Syntax like:

```
#grid::grid-area(1 / 2 / 3 / 4) {
  background-color: red; /* etc */
  /* grid-positioning properties are blacklisted */
}
```

Also some way of controlling whether or not that takes up auto-flow 
space. Might want to reserve space or not. Can we base this on 
'content' or something? Or do we need a new property?

Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/499 using your GitHub 
account