Add Mastodon "me" link to the header of the homepage on a WordPress website.

add-mastodon-link.php

<?php

/**
 * You'll need to replace
 * "https://phpc.social/@salcode"
 * with  your own Mastodon URL.
 * and place this code somewhere executible (e.g. mu-plugins)
 */
add_action( 'wp_head', function() {
	if ( ! is_front_page() ) {
		return;
	}
	echo '<link rel="me" href="https://phpc.social/@salcode" />';
	echo "\n";
});