Represents a completion value and metadata about the value. The
default metadata is ``type`` to indicate special shell handling,
and ``help`` if a shell supports showing a help string next to the
value.
Arbitrary parameters can be passed when creating the object, and
accessed using ``item.attr``. If an attribute wasn't passed,
accessing it returns ``None``.
:param value: The completion suggestion.
:param type: Tells the shell script to provide special completion
support for the type. Click uses ``"dir"`` and ``"file"``.
:param help: String shown next to the value if supported.
:param kwargs: Arbitrary metadata. The built-in implementations
don't use this, but custom type completions paired with custom
shell support could use it.