docs Add new AR docs for web

This PR adds a page with some explanation about upcoming web versions of the native AR widgets. I've currently put it next to existing AR documentation (in mobile/using-mobile-capabilities/augmented-reality), but I'm totally open to putting it elsewhere. I couldn't think of a better place to put that.

Feb 20 '24 15:02 HedwigAR

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1 out of 2 committers have signed the CLA.

:white_check_mark: ConnorLand
:x: HedwigJDoets
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Feb 20 '24 15:02 CLAassistant

Looks mostly done to me. After @takumagott weighs in with any change suggestions, then I'll merge.

Apr 04 '24 13:04 ConnorLand

Looks good to me 👍

Apr 11 '24 07:04 takumagott

Putting release date label on to remind me to add the Marketplace component URL before merging.

Apr 15 '24 13:04 ConnorLand