Added Dockerfile

[agocorona]

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[agocorona]

I included a Dockerfile which creates a image where nix-shell initializes at build time, so that the image created start quickly with nix-shell as default shell with the plutus-apps source available to be navigated with VSCode, ready for cabal build

plutus-starter sould have been the way to use docker for all the Plutus related development but the docker image provided in plutus-starter does not work with new versions of VSCode and the remote extension. Additionally. the plutus-starter image is not ready with plutus code ready for compilation.

Since a Docker box may have limited memory, I recommend cabal build -j1 to avoid memory exhaustion problems

[koslambrou]

LGTM, thanks for contributing!