Add a warning that secret argument is insecure.

diff --git a/auth.php b/auth.php
index 739123a..5c0ef9b 100644
--- a/auth.php
+++ b/auth.php
@@ -22,6 +22,7 @@ $options = getopt("c:", [
   'digits:',
   'delay:'
 ]);
+if (isset($options['secret'])) echo "!!! PODAWANIE SEKRETU JAKO ARGUMENT NIE JEST BEZPIECZNE !!!\n";
 if (isset($options['c'])) $config = load_config($options['c']); else $config = new stdClass();
 $config_default = load_config(__DIR__.'/config_default.json');