[css-pseudo-4] Add issue

Author: fantasai

css-pseudo-4/Overview.bs

@@ -934,6 +934,8 @@ Styling Highlights</h3>
     <li>[=custom properties=] [[!CSS-VARIABLES-1]] (used in ''var()'' substitutions)
   </ul>
 
+  ISSUE(11011): Should 'color-scheme' go here, or in the list of applicable properties?
+
 <!-- Add this back if for some reason someone wants to implement 'outline'?
   The outline, if supported, must be drawn
   around the union of the active portions of the <a>highlight overlay</a>