Add tracking tag to default template

default-template.html

@@ -62,6 +62,6 @@
         <p>Don't want to receive these e-mails? <a href="{{ .UnsubscribeURL }}">Unsubscribe</a></p>
         <p>Powered by <a href="https://listmonk.app" target="_blank">listmonk</a></p>
     </div>
-    <div class="gutter">&nbsp;</div>
+    <div class="gutter">&nbsp;{{ TrackView }}</div>
 </body>
 </html>