Created by: philfreo
Simple change: buttons-radio-optional behaves like buttons-radio except it allows the user to deselect a chosen button.
Basically, if you have two buttons in a buttons-radio group, by using buttons-radio-optional instead you could have a 3rd state of neither button selected.
(Reopening PR #3992 which @markdotto said was a good idea, but @fat said needed unit tests)