Doc: add documentation on kraken autocompletion
Doc: add documentation on kraken autocompletion

This only cover the "scoring" of the results. But this is where most of
our problems are.

skip ci

xlqian/navitia,patochectp/navitia,pbougue/navitia,xlqian/navitia,xlqian/navitia,kinnou02/navitia,kinnou02/navitia,Tisseo/navitia,CanalTP/navitia,kinnou02/navitia,Tisseo/navitia,pbougue/navitia,Tisseo/navitia,CanalTP/navitia,patochectp/navitia,patochectp/navitia,kinnou02/navitia,pbougue/navitia,pbougue/navitia,CanalTP/navitia,patochectp/navitia,Tisseo/navitia,Tisseo/navitia,CanalTP/navitia,CanalTP/navitia,xlqian/navitia,xlqian/navitia