added default-server configuration example

README.md

@@ -209,6 +209,7 @@ haproxy_frontend:
 haproxy_backend:
   - dashboard_backend:
       balance: source
+      default_server: "inter 2s downinter 5s rise 3 fall 2 slowstart 30s maxconn 30 maxqueue 64 weight 100"
       http_checks:
         - 'send meth GET uri /check-haproxy.php hdr Host haproxy.check-vhost.de'
         - 'expect string "All services running fine"'