open visitors header link as a blank page

Author: m-aciek

template.html.jinja

@@ -10,7 +10,7 @@
 <tr>
   <th>language</th>
   <th>build</th>
-  <th><a href="https://plausible.io/data-policy#how-we-count-unique-users-without-cookies">visitors</a></th>
+  <th><a href="https://plausible.io/data-policy#how-we-count-unique-users-without-cookies" target="_blank">visitors</a></th>
   <th>translators</th>
   <th>completion</th>
 </tr>