Add links to CHANGELOG announcement for appendHtml sanitizing

CHANGELOG.md

 ## 1.11.0
 
 ### Core library changes
 
-* In dart:html, appendHtml and insertAdjacentHtml now take validator
-  and treeSanitizer parameters, and the inputs are consistently sanitized.
+* In `dart:html`, `appendHtml` and `insertAdjacentHtml` now take `nodeValidator`
+  and `treeSanitizer` parameters, and the inputs are consistently
+  sanitized. See [45818 announcement]
+  [45818 announcement](https://groups.google.com/a/dartlang.org/forum/#!topic/announce/GVO7EAcPi6A)
 * List iterators may not throw ConcurrentModificationError as eagerly in
   release mode. In checked mode, the modification check is still as eager
   as possible.
-  [r45198](https://code.google.com/p/dart/source/detail?r=45198),
+  [r45198](https://code.google.com/p/dart/source/detail?r=45198)
 * `dart:core`
   * Add `unmodifiable` constructor to `List` -
     [r45334](https://code.google.com/p/dart/source/detail?r=45334)
   * Add `unmodifiable` constructor to `Map` -
     [r45733](https://code.google.com/p/dart/source/detail?r=45733)
   * Add `empty` constructor to `Iterable` -
     [dcf0286f](https://github.com/dart-lang/sdk/commit/dcf0286f5385187a68ce9e66318d3bf19abf454b)
 * `dart:isolate`:
   * Make the priority parameter of `Isolate.ping` and `Isolate.kill` methods
     a named parameter named `priority`.
@@ skipping 280 matching lines @@
     they will keep the Dart process alive until they time out. This fixes the
     handling of persistent connections. Previously, the client would shut down
     immediately after a request.
 
   * **Breaking change:** `HttpServer` no longer compresses all traffic by
     default. The new `autoCompress` property can be set to `true` to re-enable
     compression.
 
 * `dart:isolate`: `Isolate.spawnUri` added the optional `packageRoot` argument,
   which controls how it resolves `package:` URIs.