- fix geckodriver version used following `backend-dev-e2e` base image update
- use Prosody image `prosodyim/prosody:0.12` instead of a deprecated one
- update `pubsub` image with base image update and use of new repos names
This patch introduce new docker images, replacing the unmaintained ones which were in
sat_docs.
Images + docker-compose files are provided to use SàT backend and Libervia, but also to
integrate and configure Prosody and SàT PubSub to run end-to-end tests.