chore: explicit third parameter to decode function in README

Author: bshaffer

README.md

@@ -43,7 +43,7 @@ $payload = array(
  * https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-40
  * for a list of spec-compliant algorithms.
  */
-$jwt = JWT::encode($payload, $key);
+$jwt = JWT::encode($payload, $key, 'HS256');
 $decoded = JWT::decode($jwt, new Key($key, 'HS256'));
 
 print_r($decoded);