subscribeAnchorUpdate
Subscribes to keyboard anchor update events.
The supplied subscriber receives incremental updates whenever a keyboard anchor is added, updated, removed, or reported as loaded by the system. Use the returned Cancellable to end the subscription when updates are no longer needed.
Subscribing before calling start is recommended when callers want to observe the earliest possible updates after the tracking manager begins running.
Return
A Cancellable that unregisters this subscriber.
Parameters
subscriber
The callback that receives AnchorUpdate events for PICOKeyboardAnchors.