[css-grid] Expand issue with proposal.

Author: tabatkins

css-grid/Overview.bs

@@ -1156,6 +1156,9 @@ Repeating Rows and Columns: the ''repeat()'' notation</h4>
 
 	Issue: François suggests a way to generate "just enough" repeated columns for the number of items in the grid.
 	<a href="https://lists.w3.org/Archives/Public/www-style/2015May/0113.html">(see discussion)</a>
+	One proposal is to have two keywords instead of just one ''repeat()/auto'' keyword:
+	<css>auto-fill</css> to fill the grid with repetitions,
+	and <css>auto-fit</css> to fill the grid and then drop empty repetitions.
 
 	<div class='example'>
 		This example shows two equivalent ways of writing the same grid definition.