Add WebXR classes to browser environment

[kalegd]

I'd like to propose adding the classes from W3C candidate recommendation WebXR API Spec to the browser environment

It's currently supported by Chrome, Edge, Opera, Android, and all web browsers for VR devices such as the Meta Quest Browser, Firefox Reality, Wolvic, etc. Apple is holding out on adoption for Safari until they release their Apple Vision Pro because they don't like to play nicely with others they're working on it. It's currently available in safari behind some flags though (same with normal FireFox)