GitLab

* Cross-server double puppeting is now possible
* Python 3.9 is now supported
* End-to-bridge encryption no longer requires login_shared_secret,
  but the homeserver must support MSC2778 (Synapse 1.21+)

Handle bad attachments.

Add support for formatting in messages

Note: this is not the correct way to bridge formatting, but Hangouts
will probably be replaced by Google Chat next year, so it's not worth
it to spend time writing a proper HTML parser.
https://blog.google/products/workspace/latest-google-hangouts-and-upgrade-google-chat/

Co-authored-by: Tulir Asokan <tulir@maunium.net>

.. instead of creating a single text-only segment. This should add support for
formatting withing messages, e.g, recognising urls