security: SRI Font Awesome, CSP restrictions, remove X-XSS-Protection, rate limiting

mentions-legales.php.sample

@@ -13,7 +13,7 @@ setSecurityHeaders();
     <meta name="description" content="Consultez les mentions légales de <?php echo SITE_NAME; ?>. Informations légales, conditions d'utilisation et politique de confidentialité.">
     <link rel="canonical" href="<?php echo 'https://' . $_SERVER['HTTP_HOST'] . '/mentions-legales.php'; ?>">
     <link rel="stylesheet" href="css/styles.css?v=<?php echo filemtime('css/styles.css'); ?>">
-    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/7.0.1/css/all.min.css">
+    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/7.0.1/css/all.min.css" integrity="sha512-2SwdPD6INVrV/lHTZbO2nodKhrnDdJK9/kg2XD1r9uGqPo1cUbujc+IYdlYdEErWNu69gVcYgdxlmVmzTWnetw==" crossorigin="anonymous">
 
     <!-- Favicons -->
     <link rel="apple-touch-icon" sizes="180x180" href="img/apple-touch-icon.png">