Added Caddy2 example for securing the admin pages

Proxy-examples.md

@@ -68,6 +68,13 @@ If you prefer, you can also directly specify a value instead of substituting an
   # if you encounter issues.
   encode gzip
 
+  # Optionally only allow access to the admin interface from local networks
+  @secureadmin {
+    not remote_ip 192.168.0.0/16 172.16.0.0/12 10.0.0.0/8
+    path /admin*
+  }
+  redir @secureadmin /
+
   # Notifications redirected to the websockets server
   reverse_proxy /notifications/hub <SERVER>:3012