No support for trackpad in WMR

[BastiaanOlij]

Currently we only support a single joystick/trackpad input mapped to the analog input.

On vive this is mapped to the trackpad
On touch, wmr and index this is mapped to the joystick

WMR also has a trackpad, index controllers also have a.. well... little horizontal thingy....

We'll need to add a second analog input that is only mapped for WMR and index and outputs to an extra set of axis.

[BastiaanOlij]

On a side note, we did implement this in the OpenXR plugin and as Valve is moving to making OpenXR their main API switching over to it might be a good idea.