Fixture for Gutenberg editor

Hi

To fix multipage plugin in this evil editor you should change regexp pattern in class-mpp.php

//define( 'MPP_PATTERN', '/\[nextpage[^\]]*\]/' );
define( 'MPP_PATTERN', '/<!-- wp:shortcode -->\n?(\[nextpage[^\]]*\])\n<!-- \/wp:shortcode -->?/');

have a nice day