Documentation Update - Mention new mailing list

- Added mention of new mailing list, as a place to discuss task
  features.

html/task.html

@@ -71,6 +71,12 @@
                 which illustrates many of task's features.
               </p>
 
+              <p>
+                For the latest news, discussion of proposed task features, and
+                somewhere to voice your opinions, join us at
+                <a href="http://groups.google.com/group/taskprogram">http://groups.google.com/group/taskprogram</a>.
+              </p>
+
               <br />
               <h2 class="title">Get the Latest Stable Release</h2>