Introduced new const to easily change the sites name globally

var/www/html/upgrade.php

@@ -10,7 +10,7 @@ use chillerlan\QRCode\QROptions;
 header('Content-Type: text/html; charset=UTF-8');
 ?>
 <!DOCTYPE html><html><head>
-<title>Daniel's Hosting - Upgrade account</title>
+<title><?php echo htmlspecialchars(SITE_NAME); ?> - Upgrade account</title>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 <meta name="author" content="Daniel Winzen">
 <meta name="viewport" content="width=device-width, initial-scale=1">