KbReleaseWait waits until all keys on the keyboard are released.
It also returns if the optional deadline ‘untilTime’ is reached.
You’ll typically use this function to make sure that all keys are idle
before you start some new trial that collects keyboard responses, after
you’ve used KbCheck, KbWait or KbPressWait for collecting a response. A
different approach is to use KbStrokeWait.