Add screentop tracking mode support.

[JamesProvan-UL]

This pull request adds the option for LeapJS to select Screentop tracking mode with the newly open sourced Ultraleap Tracking WebSocket server.

Usage

Initialise screentop mode when connecting to the websocket server:

let controller = new Leap.Controller({optimizeScreentop: true}).connect();

And toggle screentop mode on / off:

controller.setOptimizeScreentop(true);
controller.setOptimizeScreentop(false);

Detail

Setting the mode to false will default back to Desktop tracking mode. You must match a setOptimizeXYZ(true); call with a corresponding setOptimizeXYZ(false); call to get back to Desktop mode. If you instead use the other optimize tracking mode call setOptimiseZYX(false); it will not change the mode to Desktop.

Screentop tracking mode was added to the now open sourced Ultraleap Tracking WebSocket which allows LeapJS support with Ultraleap Gemini V5 and above.