add diff url for version 23

git-svn-id: https://svn.apache.org/repos/asf/maven/pom/trunk@1434742 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/site-docs/apt/index.apt b/src/site-docs/apt/index.apt
index 48a2c0c..f9e7956 100644
--- a/src/site-docs/apt/index.apt
+++ b/src/site-docs/apt/index.apt
@@ -58,6 +58,8 @@
 *--------------+------------+
 || <<Version>> || <<Release Date>> ||
 *--------------+------------+
+| {{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-23/pom.xml?view=markup}23}} ({{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-23/pom.xml?r1=HEAD&r2=1371599&diff_format=h}diff}}) |  |
+*--------------+------------+
 | {{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-22/pom.xml?view=markup}22}} ({{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-22/pom.xml?r1=HEAD&r2=1157980&diff_format=h}diff}}) | 2012-08-08 |
 *--------------+------------+
 | {{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-21/pom.xml?view=markup}21}} ({{{http://svn.apache.org/viewvc/maven/pom/tags/maven-parent-21/pom.xml?r1=HEAD&r2=1134934&diff_format=h}diff}}) | 2011-08-18 |