[HttpFoundation] Add HTTP_EARLY_HINTS const

Author: ahmadmayahi

Response.php

@@ -21,6 +21,7 @@ class Response
     const HTTP_CONTINUE = 100;
     const HTTP_SWITCHING_PROTOCOLS = 101;
     const HTTP_PROCESSING = 102;            // RFC2518
+    const HTTP_EARLY_HINTS = 103;           // RFC8297
     const HTTP_OK = 200;
     const HTTP_CREATED = 201;
     const HTTP_ACCEPTED = 202;