Add previous page link for crawlers

app/views/list/list.erb

@@ -4,9 +4,15 @@
 <% end %>
 </div>
 
-<% if @list.topics.length > 0 %>
-<p><a href="<%= @list.more_topics_url.sub('.json?','?') %>" rel="next"><%= t 'next_page'%></a></p>
-<% end %>
+<p>
+  <% if params[:page].to_i > 1 %>
+    <a href="<%= @list.prev_topics_url.sub('.json?','?') %>" rel="prev" style="margin-right: 30px;"><%= t 'prev_page'%></a>
+  <% end %>
+
+  <% if @list.topics.length > 0 %>
+    <a href="<%= @list.more_topics_url.sub('.json?','?') %>" rel="next"><%= t 'next_page'%></a>
+  <% end %>
+</p>
 
 <p><%= t 'powered_by_html' %></p>