feat: added dockerfiles

[antjkennedy]

• Dockerfile added for building the project
• docker-compose.yml added to support example
• simple example configs added for convenience

[jamesdbaker]

The Dockerfile works fine, and whilst I haven't tested the docker-compose or configs they look like they should work too.

However, I'd suggest changing how the Docker aspects are documented, perhaps adding a separate file or a separate section to the README explaining how to build and use them, rather than mixing it in with the existing documentation. I think it also needs some rewording as well - at the moment, it reads like you have to run Docker Baleen via the example docker-compose.yml with the example pipeline; rather than that just being an example and actually it is run with

docker build -t baleen:2.4.1-SNAPSHOT .
docker run -d -p 6413:6413 baleen:2.4.1-SNAPSHOT

[rixsonm-dstl]

This PR looks fine, can the documentation be updated as requested above.