Add Dockerfile

[felixb]

Add a Dockerfile for using dynalite w/o nodejs.

Unlike #64, this builds from source allowing integration with docker hub by using automated builds.
This would result in having docker hub building and hosting a docker images for each tag and the current latest master/HEAD on each push.

Running dynalite in docker would look like this:

docker run --rm -p 4567:4567 dynalite

Like the real dynalite executable parameters are available:

docker run --rm -p 8123:8123 dynalite --port 8123

[ryanblock]

I'd be amenable to this, may need a few tweaks though. It's not clear from that Dockerfile how ports are configurable there (although to be honest, I'm no Docker expert). Would def want to see some tests too, and probably something around publishing to Docker Hub (which should be easy enough with GitHub Actions). wdyt?