add loading text for form submit buttons

app/views/email_settings/index.html.erb

@@ -34,7 +34,7 @@
         </div>
       <% end %>
       <div class="form-control">
-        <%= f.button button_title, class: 'base-button' %>
+        <%= f.button button_title(title: 'Save', disabled_with: 'Saving'), class: 'base-button' %>
       </div>
     <% end %>
   </div>