function enqueue_custom_scripts() {
    wp_enqueue_style('main-css', get_template_directory_uri() . '/style.css');
    wp_enqueue_script('main-js', get_template_directory_uri() . '/main.js', array('jquery'), null, true);
}
add_action('wp_enqueue_scripts', 'enqueue_custom_scripts');
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://sankaia.com/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://sankaia.com/wp-sitemap-posts-post-1.xml</loc></sitemap><sitemap><loc>https://sankaia.com/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://sankaia.com/wp-sitemap-taxonomies-category-1.xml</loc></sitemap><sitemap><loc>https://sankaia.com/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>