insert filter-search.js scripts into pages and archive templates.

The filter code was moved to its own file and these two files utilse that
code. So, these templates now must call them. The reason for moving the code out
is to stop the browser's console printing errors -- because the filter JS code
was trying to run on pages which didn't have the correct HTML.

templates/archive.html

@@ -21,4 +21,5 @@
         {% endfor %}
     </ul>
 </main>
+<script src="/js/filter-search.js"></script>
 {% endblock %}

templates/pages.html

@@ -18,4 +18,5 @@
         {% endfor %}
     </ul>
 </main>
+<script src="/js/filter-search.js"></script>
 {% endblock %}