[css-conditional-3] update changes

Author: svgeesus

css-conditional-3/Overview.bs

@@ -714,6 +714,9 @@ The following (non-editorial) changes were made to this specification since the
 <a href="https://www.w3.org/TR/2013/CR-css3-conditional-20130404/">4 April 2013 Candidate Recommendation</a>:
 
 <ul>
+  <!-- to 1 Dec 2020 -->
+  <li>Clarified that namespaces in conditionText are invalid</li>
+  <li>New editors added</li>
   <li>Added explicit call to [=CSS/parse=] rather than "matches the grammar"
   <li>Removed duplicate CSSGroupingRule, which is already defined by CSSOM
   <li>Rewrote the supports() text into algorithm form,