[css-syntax] Add the escaped surrogate change in the Changes section.

Author: SimonSapin

css-syntax/Overview.html

@@ -3003,6 +3003,10 @@ <h2 data-level=10 id=changes><span class=secno>10 </span><span class=content>Cha
 			<a data-link-type=token href=#tokendef-column>〈column〉</a> has been added,
 			to keep Selectors parsing in single-token lookahead.
 
+		<li>
+			Hexadecimal escape for <a href=#surrogate-code-point>surrogate code points</a> now emit a replacement character rather than the surrogate.
+			This allows implementations to safely use UTF-16 internally.
+
 	</ul>
 
 <p>	Parsing changes:

css-syntax/Overview.src.html

@@ -2890,6 +2890,10 @@ <h2 id="changes">Changes from CSS 2.1 and Selectors Level 3</h2>
 			<<<column>>> has been added,
 			to keep Selectors parsing in single-token lookahead.
 
+		<li>
+			Hexadecimal escape for <a>surrogate code points</a> now emit a replacement character rather than the surrogate.
+			This allows implementations to safely use UTF-16 internally.
+
 	</ul>
 
 	Parsing changes: