[css-lists-3] Add more comments to issue. #4448 (comment)

Author: fantasai

css-lists-3/Overview.bs

@@ -241,7 +241,10 @@ Properties Applying to ''::marker''</h4>
   e.g. ''::before::marker''.
 
   ISSUE: ''white-space: pre'' doesn't have quite the right behavior;
-  ''text-space-collapse: preserve-spaces'' might be closer to what's needed here.
+  ''text-space-collapse: preserve-spaces'' + ''text-space-trim: discard-after''
+  might be closer to what's needed here.
+  See discussion in <a href="https://github.com/w3c/csswg-drafts/issues/4448">Issue 4448</a>
+  and <a href="https://github.com/w3c/csswg-drafts/issues/4891">Issue 4891</a>.
 
 <h3 id='content-property'>
 Generating Marker Contents</h3>