docs(Table): add attached example

[levithomason]

This is not documented in the core SUI Table definition, however, it is shown in the examples. We've added support but need to show a similar example.

Supported added in #593.
SUI example here: http://semantic-ui.com/examples/attached.html

I've also added Semantic-Org/Semantic-UI#4615 requesting it be added to the core SUI Table definition docs.