Accommodate multiple Standards per Workstream better

[annevk]

I noticed a couple issues, both with policy and the way we operate.

https://github.com/whatwg/meta/blob/main/MAINTAINERS.md#review-drafts suggests this line which we use whenever we publish a Review Draft, e.g., whatwg/url#755:

A MONTH YEAR Review Draft (linked) for this Workstream will be published shortly after merging this pull request.

This works for a 1:1 mapping between Standards and Workstreams, but not when there's multiple. I suspect this would need to be something like

A MONTH YEAR Review Draft (linked) of the [X] Standard for the [X] Workstream will be published ...

Perhaps it could be "this Standard" as we can assume people following the repository will know. And the link also makes that clear. The Workstream is not necessarily clear however.

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In the Workstream Policy https://whatwg.org/workstream-policy we talk about a "Workstream Repository", but this is not the way the WHATWG operates. We have repositories for Standards. I suggest we pluralize the definition (i.e., allow a Workstream to have multiple repositories) and adjust references to it accordingly.

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That also suggest we might want to track repositories that don't host a Standard but do belong to a Workstream. E.g., whatwg/html-build should probably belong to the HTML Workstream. Perhaps this is a thing we should add to db.json?