Added support for enabling and disabling the three-ar component.

[RSpace]

I needed a way to enable and disable AR on the fly in the my app, so I came with this solution. It's not pretty, and it's a lot of changed and added code, I know. But I think there's a lot of value in being able to enable and disable AR mode on the scene.

[machenmusik]

Can you say more about what you're doing? My original thought was that to toggle between AR and VR, it would be easier to simply use a different camera, but if you need to reuse the same one, then I understand better why you are looking to toggle

[machenmusik]

Thanks for the PR!
From our discussion, it seems that you would indeed like to reuse the camera -- and you're probably in the vast majority there; I am thinking that maybe it would be better to refactor things slightly, so that the ar scene component introduces an ar-camera component on the appropriate camera (specified by selector), that can be enabled / disabled to effect your AR toggling.
With that in mind, I'm going to close this PR and open a corresponding issue.

[RSpace]

👍