JWK attributes for WebCrypto keys: last call

All,

On our call today we discussed the proposal for this [1] which I revised as
a result of the email/bug discussion (Comment 12 to [1]). There were no
further comments on the call and have been no further comments on the list.

We agreed to send a "last chance" email to the list (that is what this is).
In the absence of comments we'll add this material to the editor's draft.

...Mark

[1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=23796