AffiliateWP - Change the emails from plain text to HTML, filter the application accepted email

gistfile1.php

<?php

/**
 * Change the email content types to HTML
 */
function affwp_custom_email_headers( $headers ) {
	$headers[] = "Content-type: text/html";

	return $headers;
}
add_filter( 'affwp_email_headers', 'affwp_custom_email_headers' );

/**
 * Filter the application accepted email
 */
function affwp_custom_application_accepted_email( $message, $args ) {
	ob_start();
?>

	<p>Congratulations <?php echo affiliate_wp()->affiliates->get_affiliate_name( $args['affiliate_id'] ); ?>!</p>
	<p>Your affiliate application on <?php echo home_url(); ?> has been accepted!</p>
	<p>Log into your affiliate area at <?php echo get_permalink( affiliate_wp()->settings->get( 'affiliates_page' ) ); ?> </p>
	<p>Add some more HTML</p>

<?php
	return ob_get_clean();
}
add_filter( 'affwp_application_accepted_email', 'affwp_custom_application_accepted_email', 10, 2 );