Spin up local testnet with Docker

_Hypothesis: A quick and straightforward way to spin up a local testnet would positively affect the developer experience._

When looking at other blockchains, many - such as Hyperledger Fabric, Mina, Solana - have simple, reproducible steps to create a local testnet via docker.

[Plutip](https://github.com/mlabs-haskell/plutip) appears to be the simplest solution at the moment, but with a `nix build .` as the initial step, I'd argue that there is still some work ahead of us if we wanted to create a local testnet on our machines.

Even if developing dApps on Cardano was easy (it's not), this initial hurdle is pretty big.
I would like to propose an effort to containerize infrastructure that goes beyond a cardano-node docker image.