Added JIRA ticket number (850) to changelog.html

changelog.html

@@ -65,6 +65,7 @@ Upcoming changes</a>
     Added UI component to show notification bar at the top of the page
   <li class="rfe">
     Users can configure search to be case insensitive.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-850">issue 850</a>)
   <li class="rfe">
     Inline help now reports the plugin that contributes the said feature.
   <li class="rfe">