v8.9.0

Added

• VerificationMethodError and IVerificationMethodErrorCode
  (notFound | notAuthorized | invalidId): a typed error for a
  verification method that resolved but cannot back a proof, with the same
  constructor shape as DIDResolutionError plus an optional
  verificationMethod id. Thrown by @interop/jsonld-signatures and matched
  by @interop/verifier-core on name + code.