v0.19.0

Also note the v0.19.0-beta.1 changelog, there were some slightly breaking changes.

• Renamed master branch to main.
• (bridgev2) Added more features.
• (crypto) Fixed bug with copying m.relates_to from wire content to decrypted content.
• (mediaproxy) Added module for implementing simple media repos that proxy requests elsewhere.
• (client) Changed Members() to automatically parse event content for all returned events.
• (bridge) Added /register call if /versions fails with M_FORBIDDEN.
• (crypto) Fixed DecryptMegolmEvent sometimes calling database without transaction by using the non-context version of ResolveTrust.
• (crypto/attachment) Implemented io.Seeker in EncryptStream to allow using it in retriable HTTP requests.
• (event) Added helper method to add user ID to a Mentions object.
• (event) Fixed default power level for invites (thanks to @rudis in #250).
• (client) Fixed incorrect warning log in State() when state store returns no error (thanks to @rudis in #249).
• (crypto/verificationhelper) Fixed deadlock when ignoring unknown cancellation events (thanks to @rudis in #247).