radio-wombat-toolkit/inc/add-show-feed.php

<?php

function add_shows_feed() {
    add_feed( 'shows.xml', 'render_shows_feed' );
}
add_action( 'init', 'add_shows_feed' );

function render_shows_feed()    {
    load_template(dirname(__FILE__)."/../feeds/radiomanifest-shows.php" );
}

// enable cors policy for every feed
function add_header_origin() {
    if (is_feed()){
        header( 'Access-Control-Allow-Origin: *' );
    }
}    
add_action( 'pre_get_posts', 'add_header_origin' );


?>