add <hr> between sections of digest email

app/views/user_notifications/digest.html.erb

@@ -14,8 +14,10 @@
     <%= raw(t 'user_notifications.digest.why', site_link: html_site_link, last_seen_at: @last_seen_at) %>
 
     <%- if @featured_topics.present? %>
+      <hr/>
       <h3><%=t 'user_notifications.digest.top_topics' %></h3>
 
+
       <%- @featured_topics.each_with_index do |t, i| %>
         <div class='featured-topic'>
           <%= link_to t.title, "#{Discourse.base_url}#{t.relative_url}" %>
@@ -34,6 +36,7 @@
     <%- end %>
 
     <%- if @new_topics.present? %>
+      <hr/>
       <h3><%=t 'user_notifications.digest.other_new_topics' %></h3>
 
       <%- @new_topics.each do |t| %>
@@ -61,6 +64,7 @@
       <%- end %>
     <%- end -%>
 
+  <hr/>
   <span class='footer-notice'>
     <%=raw(t :'user_notifications.digest.unsubscribe',
        site_link: html_site_link,