Added scrolling threads with up and down keys

For 8chan X. Redone so it's in js folder.
@KillerWhale321

templates/index.html

@@ -86,5 +86,7 @@
 	<script type="text/javascript">{% raw %}
 		ready();
 	{% endraw %}</script>
+	
+	<script src="js/threadscroll.js"></script>
 </body>
 </html>