v0.6.0

• Updated to libsignal v0.44.0.
• Refactored bridge to support Signal's new phone number identifier (PNI) system in order to fix starting new chats and receiving messages from new users.
  • When starting a chat with a user you haven't talked to before, the portal room will not have a ghost user for the recipient until they accept the message request.
• Added support for syncing existing groups on login instead of having to wait for new messages.
• Added notices if decrypting incoming message from Signal fails.
• Added bridging of group metadata from Matrix to Signal (thanks to @maltee1 in #461).
• Added command to create new Signal group for Matrix room (thanks to @maltee1 in #461 and #491).
• Added commands for inviting users to Signal groups by phone number (thanks to @maltee1 in #495).
• Improved handling of missed Signal group metadata changes (thanks to @maltee1 in #488).