Nix Flake for Development Shell

Setting up a development environment for arti can be quite tricky. There are is not just a Rust toolchain for building, but also several system libraries which are required for the linker to succeeded. And then there is also our entire testing suite which can be quite cumbersome to setup on a new machine, which usually either involves copying install commands from .gitlab-ci or do a trial error approach, installing packages until all error messages eventually subside.

Nix offers a toolchain for Darwin and Linux based system that is centered around reproducible environments, including but not limited to development shells. Being able to get an up and running arti dev-shell by just invoking nix develop in the root repository would be very sweet.