Add Spec Skeleton

[ayuishii]

This change adds a super basic spec skeleton

• Updates metadata
• Adds IDL
• Headers of future sections to fill out

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Preview | Diff

[ayuishii]

Hi @annevk! We had a question about spec location.
Eventually we want Storage Buckets to be apart of the Storage Spec (https://storage.spec.whatwg.org/). But until then, would you recommend building this spec as a standalone here, or to build it off of the Storage Spec and create a PR?

Thanks!

[annevk]

Building it here seems easier as I expect the PR would get a lot of back-and-forth, but updating whatwg/storage#2 or new issues with some of the design decisions as you go would be good I think so people have a chance to weigh in early.