[css-conditional-3][editorial] Improve changes list.

Author: fantasai

css-conditional-3/Overview.bs

@@ -717,9 +717,27 @@ The following (non-editorial) changes were made to this specification since the
 
 <ul id="changes-20201208">
   <!-- to 6 Oct 2021 -->
-  <li>Defined feature queries ("supports" queries)</li>
-  <li>Removed the "unknown" value</li>
-  <li>Clarified placement rules</li>
+  <li>Defined the terms [=CSS feature queries=] and [=supports queries=]
+      to refer to the conditional syntax of `@supports` rules,
+      to allow better cross-referencing.
+  <li>Removed the “unknown” value in [=CSS feature queries=]’ boolean logic,
+      defining unrecognized syntaxes as “false” instead.
+      (<a href="https://github.com/w3c/csswg-drafts/issues/6175">Issue 6175</a>)
+  <li>Clarified [[#use|placement]] of [=conditional group rules=].
+      (<a href="https://github.com/w3c/csswg-drafts/issues/5697">Issue 5697</a>)
+      <blockquote>
+         <p>Conditional group rules are allowed <ins>wherever style rules are allowed
+         (</ins>at the top-level of a style sheet, <del>and inside</del> <ins>as well as within</del>
+         other conditional group rules<ins>)</ins>.
+         CSS processors must process such rules as described above.
+
+         Any <ins>at-</ins>rules that are not allowed after a style rule
+         (e.g., @charset , @import , or @namespace rules)
+         are also not allowed after a conditional group rule<del>.
+         Therefore, style sheets must not place such rules after a conditional group rule,
+         and CSS processors must ignore such rules.</del><ins>,
+         and are therefore invalid when so placed.</ins>
+      </blockquote>
 </ul>
 
 The following (non-editorial) changes were made to this specification since the