ToggleSwitchWidget: Add description, example, and mark private methods
ToggleSwitchWidget: Add description, example, and mark private methods

Change-Id: Id1dada8491ca03ded9e2cc058ac0ca99fb403e56

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui