Update for 2018-12 release

Signed-off-by: Eric Poirier <eric.poirier@eclipse-foundation.org>
diff --git a/content/en_index.php b/content/en_index.php
index 118783d..231dfee 100644
--- a/content/en_index.php
+++ b/content/en_index.php
@@ -16,10 +16,11 @@
 
 <h2>Current releases</h2>
 <ul class="fa-ul">
-  <li><a href="http://help.eclipse.org/2018-09/index.jsp"><i class="fa fa-globe"></i> Eclipse SimRel 2018-09 (4.9) Documentation</a> (HTML Help Center)</li>
+  <li><a href="http://help.eclipse.org/2018-12/index.jsp"><i class="fa fa-globe"></i> Eclipse SimRel 2018-12 (4.10) Documentation</a> (HTML Help Center)</li>
 </ul>
 <h2>Older releases</h2>
 <ul class="fa-ul">
+  <li><a href="http://help.eclipse.org/2018-09/index.jsp"><i class="fa fa-globe"></i> Eclipse SimRel 2018-09 (4.9) Documentation</a> (HTML Help Center)</li>
   <li><a href="http://help.eclipse.org/photon/index.jsp"><i class="fa fa-globe"></i> Eclipse Photon (4.8) Documentation</a> (HTML Help Center)</li>
   <li><a href="http://help.eclipse.org/oxygen/index.jsp"><i class="fa fa-globe"></i> Eclipse Oxygen (4.7) Documentation</a> (HTML Help Center)</li>
   <li><a href="http://help.eclipse.org/neon/index.jsp"><i class="fa fa-globe"></i> Eclipse Neon (4.6) Documentation</a> (HTML Help Center)</li>