Add a friendly welcome script, If there's no command being specified

It would be nice to have a script that tells the user what they can do with this image, I was thinking about some example of commands that you can run and use. This can be added by making a entrypoint script to the docker image. The entrypoint script will be executed if there's no command specified when running the container.

Start by inspecting the Docker image definition and its current command or entrypoint configuration. Add the requested welcome output for runs with no command, including example commands, and verify the image still behaves normally when a command is supplied.

Written by the indexing model from the issue text.