Toggle button (segmented button)

[mkernohanbc]

A toggle button provides a button that can switch between binary states. Used singly, they enable the user to switch a setting on or off, similarly to a switch.

Toggle buttons can also be grouped together, enabling more complex compositions. For example:

• A toolbar, enabling the user to configure multiple on/off settings
• A switcher, enabling the user to switch between two or more mutually-exclusive settings

WIP designs on Components branch in Figma

[mkernohanbc]

Initial work-in-progress (implementing ToggleButton and ToggleButtonGroup from RAC) is in draft (see #519.)

@Philip-Cheung as discussed, holding on further changes until you've finalised the design spec.