Preloading block styles to make WordPress sites faster

functions.php

<?php
/**
 * Add some preloading
 * @link: https://www.phpied.com/faster-wordpress-rendering-with-3-lines-of-configuration/
 */
function hints() {
	$wp_version = get_bloginfo( 'version' );
	header( 'link: </wp-includes/css/dist/block-library/style.min.css?ver=' . $wp_version . '>; rel=preload' );
}
add_action( 'send_headers', 'hints' );