Add an entry in the help list
ok = add_help_chapter(title,path[,mode])
:title String array, Help chapter title : :path String array, Help chapters path : :mode A boolean, if TRUE, the chapter is considered as belongs to a
internal modules, otherwise, the chapter is added as external module. It is an optional input argument and its default value is %F.
:
This function adds a new entry in the help list. If the path is already present in the help list, add_help_chapter skips the add. The function checks if the directory exist.