Update external tool when new frame is displayed in Ground Truth Labeler app
frameChangeListener( provides an
option to synchronize an external tool with the frame changes in the Ground
Truth Labeler app. The app calls this method when a new frame is displayed in the app.
If the slider is between two timestamps, then the app displays the frame that is at the
previous timestamp. For more details, see Control Playback of Signal Frames for Labeling.
The client class must implement this method.