[Web] set cookie SameSite attribute to Lax

data/web/inc/sessions.inc.php

@@ -2,6 +2,7 @@
 // Start session
 if (session_status() !== PHP_SESSION_ACTIVE) {
   ini_set("session.cookie_httponly", 1);
+  ini_set("session.cookie_samesite", "Lax");
   ini_set('session.gc_maxlifetime', $SESSION_LIFETIME);
 }