Add AggregateError to promise-any feature

[Elchi3]

I think AggregateError should belong to the promise-any feature.

This PR is also a bit of a process question: If we think that certain features should contain additional BCD keys, do we open a PR here in web-features to alter the feature's definition? (and sync the decision back to BCD later on?) or should things be synced in two ways (a PR updating tags in BCD would have been fine, too). I'm leaning towards just syncing from web-features to BCD for the moment, but curious to hear what others think.

[ddbeck]

This makes sense to me. It was also part of the same proposal, so it's likely that anything that throws AggregateError will have had Promise.any() support first. I'm just assuming though and have not checked.

[ddbeck]

This PR is also a bit of a process question: If we think that certain features should contain additional BCD keys, do we open a PR here in web-features to alter the feature's definition? (and sync the decision back to BCD later on?) or should things be synced in two ways (a PR updating tags in BCD would have been fine, too). I'm leaning towards just syncing from web-features to BCD for the moment, but curious to hear what others think.

I think in the near-term, edit here and sync back to BCD later is the correct thing to do. Long-term, I'd expect bidirectional syncing to happen, so that the edits can happen at the most immediate site of the change, but we need better release coordination and wholly automatic tools for that to be practical.

[Elchi3]

Thanks Daniel. For bidirectional syncing we need to decide which project will override the other if needed but we can discuss that at a different time. I'm going to propose updates to features via web-features for now like done in this PR.