[css-align] Add issue for handling of abspos align/justify-self when left/right is non-auto and width is auto.

Author: tabatkins

css-align/Overview.bs

@@ -738,6 +738,12 @@ Block/Cross-Axis Alignment: the 'align-self' property</h3>
 			to use shrink-to-fit sizing for calculating ''width/auto'' measures,
 			and 'align-self' dictates alignment as follows:
 
+			Issue: When you have non-auto left/right and auto width,
+			legacy behavior stretches the width and ignores margins.
+			We should keep "auto" around for abspos,
+			and have it do this legacy behavior.
+			Any other value (including "stretch") should do standard "auto margins get first dibs" behavior.
+
 			The <a>alignment container</a> is the box's containing block
 			as modified by the offset properties ('top'/'right'/'bottom'/'left').
 			The <a>alignment subject</a> is the box's margin box.