This is an easy fix, will include a PR in a bit.

Preconditions

1. Current docker-compose doesn't expose 3306

Steps to reproduce

1. Bring up docker
2. Notice the port is not exposed using docker-compose ps

Expected result

1. It should look like this

magento-m2_db_1 docker-entrypoint.sh mysqld Up 0.0.0.0:3306->3306/tcp

Actual result

1. Not exposed

magento-m2_db_1 docker-entrypoint.sh mysqld Up