knorm-postgres: Docker PostgreSQL tools for knorm

knorm-postgres provides Docker-based PostgreSQL management commands (start, stop, remove) for testing knorm ORM and its plugins. Version 2.0.0 is the latest stable release, with infrequent updates. It simplifies setting up disposable PostgreSQL containers for integration tests, defaulting to port 5616 and credentials knorm/knorm. Unlike general Docker tools, it is tightly coupled with knorm's testing workflow.