function avelo_phase53_styles(){
    wp_enqueue_style(
        'avelo-main',
        get_stylesheet_uri(),
        array(),
        '6.0.8'
    );
}
add_action('wp_enqueue_scripts','avelo_phase53_styles',99);

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://avelo.digital/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://avelo.digital/wp-sitemap-posts-post-1.xml</loc></sitemap><sitemap><loc>https://avelo.digital/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://avelo.digital/wp-sitemap-taxonomies-category-1.xml</loc></sitemap><sitemap><loc>https://avelo.digital/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>