re-add api route

app/templates/threads/thread.html

@@ -72,5 +72,16 @@
     </span>
   </div>
 </dialog>
+<input type='hidden' id='thread-subscribe-endpoint' value='{{ url_for('api.thread_updates', thread_id=thread.id) }}'>
+<div id="new-post-notification" class="new-concept-notification hidden">
+  <div class="new-notification-content">
+    <p>New post in thread!</p>
+    <span class="notification-buttons">
+      <button id="dismiss-new-post-button">Dismiss</button>
+      <a class="linkbutton" id="go-to-new-post-button">View post</a>
+      <button id="unsub-new-post-button">Stop updates</button>
+    </span>
+  </div>
+</div>
 <script src="/static/js/thread.js?v=1"></script>
 {% endblock %}