feat: Link the "Help" and "Contact Us" buttons on webpage (#107)

Author: barbeau

gtfs-realtime-validator-webapp/src/main/resources/webroot/index.html

@@ -24,9 +24,8 @@
         </div>
         <div class="collapse navbar-collapse">
             <ul class="nav navbar-nav pull-right">
-                <li><a href="#">About</a></li>
-                <li><a href="#">Help</a></li>
-                <li><a href="#">Contact Us</a></li>
+                <li><a href="https://github.com/MobilityData/gtfs-realtime-validator/blob/master/TROUBLESHOOTING.md">Help</a></li>
+                <li><a href="https://bit.ly/mobilitydata-slack">Contact Us</a></li>
             </ul>
         </div>
         <!--/.nav-collapse -->