Add "Mark this page as read" to the bottom

This better matches the most common use case for the "Mark this page as
read" link, which is to click it once you have reached the bottom of the
page. Especially on mobile, it can be annoying to scroll to the top of
the page to click the link.

template/html/unread_entries.html

@@ -34,6 +34,15 @@
         </article>
         {{ end }}
     </div>
+    <section class="page-footer">
+        {{ if .entries }}
+        <ul>
+            <li>
+                <a href="#" data-on-click="markPageAsRead">{{ t "Mark this page as read" }}</a>
+            </li>
+        </ul>
+        {{ end }}
+    </section>
     {{ template "pagination" .pagination }}
 {{ end }}