New Container: Db2 #672

What is the new container you'd like to have?

IBM Db2 database.
Container: ibmcom/db2
Documentation: deployments-db2-community-edition-docker

Why not just use a generic container for this?

I noticed there is a PR #321 for the Db2 support, but it has been closed.

IBM Db2 is a widely used relational database, and it should be supported as a dedicated container.
The Db2 container requires specific setup configurations as listed in https://hub.docker.com/r/ibmcom/db2, and the wait strategry involves checking the availability of the database or some specific keywords in the container log.

Other references:

Include any other relevant reading material about the enhancement.