How to add post featured image to RSS item tag?

I am able to add a post featured image to the RSS feed like so:

function insertThumbnailRSS($content) {
    global $post;
    if(has_post_thumbnail($post->ID)){
        $content="".get_the_post_thumbnail($post->ID, 'thumbnail', array('alt' => get_the_title(), 'title' => get_the_title(), 'style' => 'float:right;')).''.$content;
    }
    return $content;
}
add_filter('the_excerpt_rss', 'insertThumbnailRSS');
add_filter('the_content_feed', 'insertThumbnailRSS');

However, upon examining the XML generated for the RSS feed, I noticed it sticks the featured image into the XML description item tag.

How can I insert post featured image into it’s own RSS feed item tag of let’s say “image”, rather than just inserting it in with the post’s content?

You could do it by adding an action to the hook ‘rss2_item’ like so:

add_action('rss2_item', function(){
  global $post;

  $output="";
  $thumbnail_ID = get_post_thumbnail_id( $post->ID );
  $thumbnail = wp_get_attachment_image_src($thumbnail_ID, 'thumbnail');
  $output .= '<post-thumbnail>';
    $output .= '<url>'. $thumbnail[0] .'</url>';
    $output .= '<width>'. $thumbnail[1] .'</width>';
    $output .= '<height>'. $thumbnail[2] .'</height>';
    $output .= '</post-thumbnail>';

  echo $output;
});