Goal: Create a docker setup that can be used for "offline" development and testing (similar to GitHub codespaces)

I have created a simple docker image that can be used for "offline" phpBB development and testing.

This setup is almost identical to the existing GitHub code spaces except it does not require GitHub account and does not consume any "cloud" time.

I have used the existing `.devcontainer` as the "source of truth", this way the docker version should be almost a 1:1 copy and require little to no changes between testing/developing using codespaces or the docker environment.

When the docker image is built, you can spin up a container that will serve live version of the phpBB that can be used for development and/or testing.