Add docker model ps

[doringeman]

You can launch docker/model-runner#42 using make docker-run.

$ MODEL_RUNNER_HOST=http://localhost:8080 docker model run ai/smollm2 hi
Hello, I'm here to help you with any questions or tasks related to Python programming. What can I assist you with today?
$ MODEL_RUNNER_HOST=http://localhost:8080 docker model ps
MODEL NAME  BACKEND    MODE        LAST USED
ai/smollm2  llama.cpp  completion  3 seconds ago

[crazy-max]

Needs rebase to make sure #62 is taken into account

[doringeman]

Fixed docs in #67.