v0.8.0-rc1

• Added support for cross-server double puppeting (thanks to @ShadowJonathan in #26).
• Added support for receiving ephemeral events pushed directly (MSC2409)
• Added opt_prometheus utility to add support for metrics without a hard dependency on the prometheus_client library.
• Bridge command system improvements (thanks to @witchent in #29, #30 and #31)
  • CommandEvents now know which portal they were ran in. They also have a main_intent property that gets the portal's main intent or the bridge bot.
  • CommandEvent.reply() will now use the portal's main intent if the bridge bot is not in the room.
  • The needs_auth and needs_admin permissions are now included here instead of separately in each bridge.
  • Moved set-pl command from mautrix-telegram.
• Switched to using yarl instead of manually concatenating base URL with path.
• Switched to appservice login (MSC2778) instead of shared secret login for bridge bot login in the end-to-bridge encryption helper.
• Changed replies to use a custom net.maunium.reply relation type instead of m.reference.