Dancer2::Plugin::Path::Class exports the keyword 'ls'
returning a Path::Class object.

The 'ls' keyword also sets some 'vars'.
- ls_name: The basename of the path
- ls_cdup: The parent of the request path
- ls_dirs: A list of subdirectories if the path is a directory object
- ls_files: A list of files or just one file if the path is a file object
