feat: enable E2E mirror creation and hosting through Docker

[galargh]

This PR takes the docker build from:

In the future it will be end-to-end blackbox that takes ZIM and spits out CID and repo.

to:

It is an end-to-end blackbox that takes mirrorzim.sh arguments, spits out CID and runs IPFS daemon.

It also updates the Dockerfile so that it reflects the instructions from the README.