[CheckboxGroup] Add `variant="table"` to match RadioGroup variants

[TribeWeb]

Description

The new CheckboxGroup component lacks the table variant found on the RadioGroup component. Since these components will often appear together in forms, it would be preferable to have the table variant for both of them.

This is already easily achieved with the new component by adding the RadioGroup styles to the item ui prop. I think it should be possible to make this change just by adding the styles to checkbox-group.ts. I'm happy to make a pull request and make the changes.

Additional context

No response