Add Dockerfile back

[emfox]

When I noticed the Dockerfile we had previously created for Devcoin v0.8.x was missing from the repository, I took the initiative to upgrade it to support Devcoin v22.0.

https://github.com/emfox/core/blob/emfox_rewrite_dockerfile/examples/Dockerfile

Since the original maintainer (osixia) has discontinued maintenance of his Docker image, I buit a new one based on the development branch of his repository.
The resulting images has been published to Docker Hub for community access.

emfox/light-baseimage:1.3.4
emfox/devcoin:latest

[emfox]

https://github.com/emfox/core/blob/master/Dockerfile
or this same file if you don't care the diff/changelog.