Add links preload for bitrix

addLinksPreload.php

<?php
\Bitrix\Main\EventManager::getInstance()->addEventHandler('main', 'OnEndBufferContent', 'addLinksPreload');
function addLinksPreload(&$content)
{
    global $USER, $APPLICATION;
    if ((is_object($USER) && $USER->IsAuthorized()) || strpos($APPLICATION->GetCurDir(), '/bitrix/') !== false) return;

    $arAdd = [];
    $arMatches = [];

    preg_match_all('/<link.+?href="(.+?\.css\?\d+)"[^>]*>/', $content, $arMatches);
    if (!empty($arMatches[1])) {
        foreach ($arMatches[1] as $sSrc) {
            $arAdd[] = '<link href="' . $sSrc . '" rel="preload" as="style">';
        }
    }

    preg_match_all('/<script.+?src="(.+?\.js\?\d+)"[^>]*><\/script\>/', $content, $arMatches);
    if (!empty($arMatches[1])) {
        foreach ($arMatches[1] as $sSrc) {
            $arAdd[] = '<link href="' . $sSrc . '" rel="preload" as="script">';
        }
    }

    if ($arAdd) {
        $content = preg_replace('/<\/title>/', '</title>' . PHP_EOL . implode(PHP_EOL, $arAdd), $content, 1);
    }
}