[cs-grid] Fix missing justify-self correction.

Author: tabatkins

css-grid/Overview.bs

@@ -3165,7 +3165,8 @@ With a Grid Container as Parent</h3>
 	However, if the <a>grid container</a> parent is also the generator of the absolutely positioned element's <a>containing block</a>,
 	instead use the <a>grid area</a> determined in [[#abspos-items]].
 	For the purpose of calculating this static position,
-	a value of ''align-self: auto'' is treated identically to ''align-self/start''.
+	a value of ''align-self/auto'' for 'align-self'/'justify-self'
+	behaves as ''align-self/start''.
 
 	Note: Note that this position is affected by the values of 'justify-self' and 'align-self' on the child,
 	and that, as in most other layout models,