Update email “content type” sent by wp_mail()

Modify email “content type” sent through wp_mail() function, from ‘text/plain’ to ‘text/html’, using ‘wp_mail_content_type’ filter.

function update_wp_mail_content_type( $content_type ) {
	return 'text/html';
}
add_filter( 'wp_mail_content_type', 'update_wp_mail_content_type', 10, 1 );