Doc: add \inherits JumpListItem

These QML types inherit the JumpListItem type.

Change-Id: I08bb2aa02af8d639253306c3f835d096f1912d3b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>