[css-scroll-snap] Add issue wrt removing 'edges' value

Author: fantasai

css-scroll-snap/Overview.bs

@@ -537,6 +537,8 @@ Scroll Snapping Alignment: the 'scroll-snap-align' property {#scroll-snap-alignm
 			Both start alignment and end alignment of this box's <a>scroll snap area</a>
 			within the <a>scroll container</a>'s <a>snap viewport</a>
 			are valid <a>snap positions</a>.
+
+			Issue: It's not 100% clear if this value is necessary, given handling for <a href="#snap-overflow">over-large elements</a>.
 	</dl>
 
 	If the element's <a>scroll container</a> is set to ''point'',