function MODULENAME_editor_js_settings_alter(array &$settings) {
  foreach (array_keys($settings['editor']['formats']) as $text_format_id) {
    /* if ($settings['editor']['formats'][$text_format_id]['format'] == 'full_html') { */
    if ($settings['editor']['formats'][$text_format_id]['editor'] == 'ckeditor5') {
      $settings['editor']['formats'][$text_format_id]['editorSettings']['config']['heading']['options'] = array(
        array(
          'title' => 'Introduction Paragraph',
          'class' => 'iac-introduction',
          'model' => 'introparagraph',
          'view'  => array(
             'name' => 'p',
             'classes' => 'iac-introduction',
          ),
          'converterPriority' => 'high',
        )
      );
    }
  }
}