Hello,
The easiest approach is to create a DOCX with the that list style and use this method:
/**
* Imports an existing list style from an existing docx document.
*
* @access public
* @example ../examples/easy/ImportListStyle.php
* @param string $path. Must be a valid path to an existing .docx, .dotx o .docm document
* @param int $id. The id of the style you want to import. You may obtain the id with the help of the parseStyle method
*/
public function importListStyle($path, $id, $name)
Regards.