Create a did:webvh test suite

[swcurran]

It would be good to have a did:tdw test suite, either in this repo or in a separate repo. Proposal:

• A folder of test cases
• Each test case in its own folder
• A readme describing the test case and, if any, special features
• A folder (or JSON doc?) for each version (or perhaps naming?) with:
  • The DIDDoc with either the {SCID} placeholder for the first version, or the proper ID for the DIDDoc
  • The parameters
  • The keypairs (public and private) needed for authorization -- for all of updateKeys, nextKeyHashes and Witness Keys
  • The timestamp to put on the version
  • The did.jsonl at the conclusion of the processing.

A registrar implementation would iterate through the test cases, and demonstrate that it can produce the same did.jsonl file. A resolver would pick up the did.jsonl files and verify their accuracy.

These are not hard requirements -- just suggestions. The first implementer can adjust the structure as needed.