[css-grid-2] Link to GH issue.

Author: fantasai

css-grid-2/Overview.bs

@@ -287,7 +287,8 @@ Aspect-ratio&ndash;controlled Gutters</h2>
 	Issue: There's a desire for having row and column gaps maintain a particular aspect ratio.
 	This is one proposal for doing so; other ideas are welcome.<br>
 	Possible extension: allow aspect ratio multipliers on 'row-gap' and 'column-gap' as well (not really useful except if you're using percents).<br>
-	Possible variation: use an `ar` unit instead of bare <<number>>s.
+	Possible variation: use an `ar` unit instead of bare <<number>>s.<br>
+	See discussion in <a href="https://github.com/w3c/csswg-drafts/issues/1116">Issue 1116</a>.
 
 	<pre class="propdef">
 	Name: align-content, justify-content