Add a changelog entry for the AppEngine compatibility.

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,11 @@
 * Table of contents
 {:toc}
 
+## 2.2.3
+
+Haml 2.2.3 adds support for the JRuby bundling tools
+for Google AppEngine, thanks to [Jan Ulbrich](http://github.com/ulbrich).
+
 ## [2.2.2](http://github.com/nex3/haml/commit/2.2.2)
 
 Haml 2.2.2 is a minor bugfix release, with several notable changes.