v0.9.21

• Added liveness and readiness endpoints to appservices.
  • The endpoints are the same as mautrix-python: /_matrix/mau/live and /_matrix/mau/ready
  • Liveness always returns 200 and an empty JSON object by default, but it can be turned off by setting appservice.Live to false.
  • Readiness defaults to returning 500, and it can be switched to 200 by setting appservice.Ready to true.