[css-cascade-3] Add changes list.

Author: fantasai

css-cascade-3/Overview.bs

@@ -955,6 +955,16 @@ Changes</h2>
 <h3 id="changes-2016">
 Changes Since the 19 May 2016 Candidate Recommendation</h3>
 
+	The following changes were made to this specification since the
+	<a href="https://www.w3.org/TR/2018/CR-css-cascade-3-20180828/">28 August 2018 Candidate Recommendation</a>:
+
+	<ul>
+		<li>
+			Clarify that ''@import'' ordering requirements are only in consideratin of valid rules.
+		<li>
+			Clarify that [=computed values=] are not serialization strings, but abstract data.
+	</ul>
+
 	The following non-trivial changes were made to this specification since the
 	<a href="https://www.w3.org/TR/2016/CR-css-cascade-3-20160519/">19 May 2016 Candidate Recommendation</a>: