update changelog

documentation/changelog.html

@@ -48,6 +48,7 @@
    <li>Students also can export documents to pdf</li>
    <li>Easy enabled for spellcheck button on web editor (Feature #2207)</li>
    <li>Increased control by platform administrator on the visibility of the folders in the documents tool (Feature #2164,#2484)</li>
+   <li>Mp3 audio files generation from a text. Mp3 audio files generation from a text. Teachers, students (into his/her user folder) and groups can create and save mp3 audio files from a text through external service support speech synthesis of Google (build and save) and vozMe (build and download)(Feature #2497)</li>
 </ul>
 <h3>Debugging</h3>
 <ul>