Add device selection explainer

[zolkis]

An initial draft to summarize the discussion.
Feel free to change it in any way, add commits here etc.

The main forums to discuss this are #749 and #759.
After we agree on a solution, this explainer can be archived.

@anssiko should we create an explainers folder?

[anssiko]

@zolkis thanks for this explainer! There's no good way to redirect existing explainers, so for consistency you can keep this file in the root. Perhaps explainer-device-selection.md -> device-selection-explainer.md.

[zolkis]

@mwyrzykowski could you please check if this is acceptable for merging, and whether the Minimum Viable Solution in the end is a good first step for making a PR (minus including the "low-latency" option which is a possible future discussion, but not now).

[mwyrzykowski]

Thank you @zolkis for the writeup! Looks good!

[huningxin]

LGTM!

[fdwr]

👍 Thanks for collecting the backstory and previous context links. If it was easy, we would have figured it out long ago, implying it's not easy 😉.

[zolkis]

Thanks @fdwr for the suggestions and comments, I have updated the text. Maybe it needs a proofreading before squash-merging.

[fdwr]

@zolkis: 👍 LGTM.

Waiting on any other input? Otherwise we'll merge it.

[zolkis]

We agreed on the last call that it could be merged - so go ahead, thanks!

[anssiko]

I did a proofreading pass with some suggestions. Also added a "Participate" header.

As discussed on our call https://www.w3.org/2025/01/16-webmachinelearning-minutes.html#f000 this explainer is now ready to be merged.

Thank you @zolkis for putting this explainer together and everyone for your review and suggestions!

As usual, this doc will be updated whenever the group learns more about this topic.

[zolkis]

Thank you Anssi!