This implements the feedback from 2 separate community workshops, the
recordings of which can be found here:

 - https://www.youtube.com/watch?v=X3XdQZx_TyU
 - https://www.youtube.com/watch?v=bBQMF6Dr6HY

In particular, this limits the scope of what this CIP tries to achieve,
and answers many of the open questions. There are still a few small
items to finish off before we're ready to merge this.

Provides a JSON-LD and JSON Schema file for the minimal features.

Reworks the wording of many bits, especially to reference a parallel CIP
to extend CIP-0013.

Renames "justification" to "comment", to leave it more general so others
can specify the rationale-related extensions.

Provides example test vectors.

Folds the "augmentation" concept into a simple "references" field.

Co-authored-by: Ryan Williams <[email protected]>