Add custom RSS feed to Wordpress

gistfile1.php

function get_me_the_email_feed_template() {
  add_filter('the_content_feed', 'css_tricks_super_awesome_feed_image_magic');
  include(ABSPATH . '/wp-includes/feed-rss2.php' );
}

function css_tricks_super_awesome_feed_image_magic($content) {
  // Weirdness we need to add to strip the doctype with later.
  $content = '<div>' . $content . '</div>';
  $doc = new DOMDocument('1.0', 'utf-8');
  $doc->LoadHTML('<?xml encoding="UTF-8">' . $content);
  $images = $doc->getElementsByTagName('img');
  foreach ($images as $image) {
    $image->removeAttribute('height');
    $image->setAttribute('width', '320');
  }
  // Strip weird DOCTYPE that DOMDocument() adds in
  $content = substr($doc->saveXML($doc->getElementsByTagName('div')->item(0)), 5, -6);
  return $content;
}