New set of Firebird docker images

We received a note from Fabio Augusto Dal Castel about a new set of docker images for Firebird.

An entirely new set of Docker images for Firebird is now available at ghcr.io:

https://ghcr.io/fdcastel/firebird

These images were written from scratch, are covered by automated tests, and are aligned with the best practices for other RDBM Docker images.