Converts links to https://gist.github.com in Gutenberg into embeds

gists_in_gutenberg.php

//Gist embeds in Gutenberg, quick fix
//Works if you add https://gist.github.com links as regular links 
add_filter( 'the_content', 'gist_in_gutenberg' );
function gist_in_gutenberg( $content ) {
	$doc = new DOMDocument();
	$doc->loadHTML($content);
		foreach ($doc->getElementsByTagName('a') as $link){	
			$href = $link->getAttribute('href');
			if (strpos($href, 'gist.github.com') !== false) {
				$element = $doc->createElement('script');
				$element->setAttribute('src',$href.'.js');
				$link->parentNode->appendChild($element);
				$links_to_remove[] = $link;	
			}
		}
		foreach ($links_to_remove as $link) {
			$link->parentNode->removeChild($link); 
		}
	$content = $doc->saveHTML();
    return $content;
}