add unread count to thread title in topic view and thread view

app/templates/threads/thread.html

@@ -12,7 +12,7 @@
 {% endif %}
 <main>
   <nav class="darkbg">
-    <h1 class="thread-title">{{ thread.title }}</h1>
+    <h1 class="thread-title">{{ thread.title }}{% if unread_count is not none %} ({{ unread_count }} unread){% endif %}</h1>
     <span>Posted in <a href="{{ url_for("topics.topic", slug=topic.slug) }}">{{ topic.name }}</a>
     {% if thread.is_stickied %}
       &bullet; <i>stickied, so it's probably important</i>