Switch to Nix #34

Benefits (incomplete list):

• I can get dependency updates ala Dependabot with an action like https://github.com/marketplace/actions/nix-flake-update (this does not seem to exist for Homebrew)

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Two main options I can see:

• https://github.com/devcontainers/features
  • https://github.com/devcontainers/features/tree/main/src/nix
• https://github.com/xtruder/nix-devcontainer

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Tasks:

• Create orphan nix branch for experimentation

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Investigate later:

• https://marketplace.visualstudio.com/items?itemName=brettm12345.nixfmt-vscode
  • Other extensions?