add loading text for form submit buttons

app/views/invitations/edit.html.erb

@@ -19,7 +19,7 @@
       </div>
     </div>
     <div class="form-control">
-      <%= f.submit 'Save password and Sign in', class: 'base-button' %>
+      <%= f.button button_title(title: 'Save password and Sign in', disabled_with: 'Saving'), class: 'base-button' %>
     </div>
   <% end %>
 </div>