XWIKI-20657: Provide a UI for the What's New feature

* Make the UIX synchronous since it's a link inside the drawer and it doesn't make much sense to be displayed after the drawer menu is open.

xwiki-platform-core/xwiki-platform-whatsnew/xwiki-platform-whatsnew-ui/src/main/resources/WhatsNew/Code/NewsUIX.xml

@@ -160,7 +160,7 @@
       <async_context/>
     </property>
     <property>
-      <async_enabled>1</async_enabled>
+      <async_enabled>0</async_enabled>
     </property>
     <property>
       <content>{{velocity}}