Moving Hand Tracking into the Working Group

Hi Everyone,

The hand tracking API <https://github.com/immersive-web/webxr-hand-input>
has settled down and it even has two implementations which is super cool.
So it's about time to move it into the working group.

This email marks the intent to move in a week's time, please reply to this
email or let myself or one of the other chairs know if you have any
objections to it being moved.

It will also be brought up again during the next WG call.

Thank you everyone who is working on the hand tracking API. It's very
exciting.

Ada