Add Spectrum CheckboxGroup component (#1003)
* Add Spectrum CheckboxGroup component
* Rename checkboxGroupProps to groupProps to match ARIA role
* Improve handling of individual checkbox props within a group
* lint
* Add docs for Spectrum CheckboxGroup
* Hide docs from prod build that are not yet released
* Add docs for useCheckboxGroup
* review updates
* Apply suggestions from code review
Co-authored-by: Danni <drobinson@livefyre.com>
Co-authored-by: Danni <drobinson@livefyre.com>
