Use X-Forwarded-For in nginx example (#1534)

it supplies HASS with the users real ip address

source/_ecosystem/nginx.markdown

@@ -124,6 +124,7 @@ http {
             proxy_set_header Host $host;
             proxy_redirect http:// https://;
             proxy_http_version 1.1;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header Upgrade $http_upgrade;
             proxy_set_header Connection $connection_upgrade;
         }