add community representatives to front page

I don't know how to preview the site locally (that's scala#38), so
perhaps my HTML is mangled -- someone should check that before
merging

partially addresses scala#56

/cc @bvenners @tpolecat

Author: SethTisue

_layouts/frontpage.html

@@ -384,6 +384,12 @@ <h2>Brought to you by</h2>
               -->
             </div>
             <div class="col-md-12 text-center">
+              <span class="subtitle col-sm-12">Community representatives:</span>
+              <div class="text-center back-level clearfix">
+                <a href="https://github.com/bvenners" class="col-md-4 col-xs-12" target="_blank">Bill Venners</a>
+                <a href="https://github.com/tpolecat" class="col-md-4 col-xs-12" target="_blank">Rob Norris</a>
+              </div>
+              <p>For information on the community representatives, see <a href="https://www.scala-lang.org/blog/2019/03/18/announcing-new-community-representative.html">this blog post</a>.
               <span class="subtitle col-sm-12">Backer-level members:</span>
               <div class="text-center back-level clearfix">
                 <a href="https://twitter.com/andy1138" class="col-md-4 col-xs-12" target="_blank">Andy Hicks</a>