Create a play with docker button

We should have a button that sets up a small docker swarm cluster in play with docker so users can try janusgraph out. A quick how to article or video on interacting with this environment would be a nice touch as well.

No files, tests, or entry points are named. Start by locating the repository's existing deployment or demo documentation and any Play with Docker integration, then define done as a working button that creates a small Docker Swarm JanusGraph environment and provides the requested how-to article or video.

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