Prepare release 2.9 (NFD 22.02)

Change-Id: I95b6f5fcdbd5fb5e965f3f65c7841344498aed22
diff --git a/docs/source/_templates/indexcontent.html b/docs/source/_templates/indexcontent.html
index c5810a1..71a7eb9 100644
--- a/docs/source/_templates/indexcontent.html
+++ b/docs/source/_templates/indexcontent.html
@@ -59,8 +59,9 @@
       <td width="50%" valign="top">
         <h2>ndnSIM Versions</h2>
         <div class="tile">
-          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.8</a><br/>
+          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.9</a><br/>
               <span class="linkdescr">the latest version</span></p>
+          <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.8/">ndnSIM 2.8</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.7/">ndnSIM 2.7</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.6/">ndnSIM 2.6</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.5/">ndnSIM 2.5</a><br/>