adding docker readme

[xuedi]

I was trying to get mapCrafter running, but the documentation is pointing to the original project, and if i understand correctly with your 1.13 changes some configs changed.

Maybe we can get a basic howto specially how to use your container by adding a docker.md with a basic config file example and a basic CLI command how to start the docker

this fork also points to the original wiki & docu, i noticed some of that infos are not up to date anymore, maybe its time for a proper fork (rename & new docu and stuff) not sure if the original creator might welcome your changes merged back ...

[miclav]

Hi
You're absolutely right. Doc needs to be updated, including the docker image available.
Thanks for opening an issue, we will track that.
M'L