Elision in DID document

Hey,

On the DIDWG call yesterday there was a discussion around selective
disclosure and elision for DID document.

It got me thinking about what a minimal effort approach to supporting
elision in DID documents might look like.

I put my thoughts together here: https://hackmd.io/@wip-abramson/rk-x9Kln1l

TLDR: I think we could just define a new type or types in a DID extension
that would enable a form of elision.

Interested what folks think, is this worth pursuing or just plain wrong :)

Cheers,
Will