v8.2.0

Added

• didKeySigner(): a signer for the key pair named under its own did:key
  (did:key:<publicKeyMultibase>#<publicKeyMultibase>), regardless of the key
  pair's id and controller, which it leaves unmodified. A key generated from
  a seed can sign without an id being set first, and a key loaded under another
  DID can still sign as its bare did:key.