ATAG brief - review and suggestions

Hi everyone, as mentioned on our weekly call I was going to do some edits
of the briefs via a Word document so I can put in comments as well as edits
that are accessible and more easily generated than GitHub tickets.

I started with "Social Media" just because I grabbed a random one, and I'll
ultimately take a pass at each one, but I'll have to come back to it on
Monday. Nonetheless, in case folks are working over the weekend here's the
Social Media one which includes comments both for that subject as well the
more general layout.

I'm not sure who is on the "WAI editors" email list so I've cc'ed everyone
I thought was involved and feel free to have me drop your individual email
if this is sending you 2 messages.

Regards,
Michele

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