Write an awesome doc for Docker, Docker Compose, and everything else in this domain. You can find invaluable examples and explanations here. I am trying to keep it up to date and relevant too. BTW if you also have a cool idea, or example open a PR/issue/discussion.
To initialize your database you can write custom bash scripts and map them to /docker-entrypoint-initdb.d directory as the docs had explained here. You can find a nice example of this here.