feat: Support XEP-0490: Message Displayed Synchronization
This depends on python-nbxmpp!84 (merged)
Adds support for XEP-0490: Message Displayed Synchronization
This uses the current implementation of read state in gajim, ie, it only works when receiving events for the latest message in a chat. This could be improved but is out of scope of this MR.
Edited by Philipp Hörist