Add Postgres Message Queue Extension

[mawandm]

Is your feature request related to a problem? Please describe.
I'm always frustrated when I have to use another system for a message queue.

Describe the solution you'd like
I'd like to have a message queue within Postgres

Describe alternatives you've considered
Alternatives are creating a message queue manually or adding a message extension manually. I'd like to have this in a managed docker image.

Additional Context
A message queue extension for Postgres is open-sourced here