privacy: set Referrer-Policy: no-referrer

- prevents third parties i link to from knowing you came from my site

templates/nginx/site.conf

@@ -7,6 +7,7 @@ server {
 
     location / {
         add_header Permissions-Policy interest-cohort=();
+        add_header Referrer-Policy: "no-referrer";
         try_files $uri $uri/ =404;
     }
 }