Add Zulip in the Welcome page.

templates/front/welcome.html

@@ -494,6 +494,13 @@
             </div>
         </div>
         {% endif %}
+
+        <div class="col-lg-2 col-md-3 col-sm-4 col-xs-6">
+            <div class="integration">
+                <img src="{% static 'img/integrations/zulip.png' %}" class="icon" alt="" />
+                <h3>Zulip<br><small>Chat</small></h3>
+            </div>
+        </div>
     </div>
 
     <div class="row tour-section">