shortcode to display hrml

my-custom-code.php

<?php
/*
Plugin Name:  My Custom Code
Plugin URI:   https://fullworks.net/
Description:  Custom code plugin
Version:      1.0
Author:       Alan
Author URI:   https://fullworks.net/
License:      GPL2
*
* No warranty or liability accepted as per GPL
*/
/**
 *
 * Shortcode to add get html for a remote source
 *
 * Usage:
 * [display_page url="http://example.com"]
 *
 * simple version no error checking etc
 */
function my_custom_shortcode( $atts ) {
	$a = shortcode_atts( array(
		'url' => '',
	), $atts );
// decode url if it was encode
	$a['url'] = urldecode($a['url']);
	$html=file_get_contents($a['url']);
//  can check for errors here
//  add code if headers need to be stripped etc to manipulate the dom using $html
	return $html;
}
add_shortcode( 'display_page', 'my_custom_shortcode' );