Dockerise Node examples

[nickw1]

Many thanks to @MikiDi for dockerising the PHP examples.

The new Node.js server will probably be easier for developers to get up and running with, but could still benefit from dockerisation, so this is a TODO.

[MikiDi]

I saw you recently took this up again. 🙏 My personal first TODO is to write out the API-specification in OpenAPI-format. That way we have something common that different implementations can work toward. I'll keep you posted ;-)

[nickw1]

@MikiDi many thanks! :-)