Three.js renderer options

[Smidgens]

It would be great if more options pertaining to the three.js WebGLRenderer were exposed in the videojs-vr config object for performance reasons.

Notable options include:

• Anti-aliasing
• Power Preference

Antialiasing for example seems to be enabled at all times:
https://github.com/videojs/videojs-vr/blob/main/src/plugin.js#L662

As far as I can tell, the renderer interface doesn't provide any setter functions to modify these properties post initialization, so even if you grab a reference to the renderer through the player (player.vr().renderer), there's still no way to tweak these options.

Even just having one property called customRendererOptions added to the videojs-vr options object would be sufficient, to allow the user to override any property at his own risk, and perhaps free the maintainers of this project from needing to maintain explicit parity with the three.js interface.

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Edit: See PR #259