[WEBXR] added option to pass WebXR Session options

[arthurlebourg]

WebXR can accept some options for hit testing, depth sensing etc. In order to use those, we need to initialize those options by passing arguments to the navigator.xr.requestSession() method which is called within the {AR/VR}Button.createButton().

Is was not possible to pass the options to the builder so I fixed that.

Yours truly, Arthur Le Bourg