Lints and suggestions for the Nix programming language

rewrite flake master

- use flake-parts - formatting with treefmt-nix - mightyiam/files to generate a new GH Actions workflow - flake-parts dev partition - comprehensive flake checks - git hooks - bump inputs - should be backwards compatible - new non-dev inputs that users might notice: - flake-parts (all the partitions trickery in the world cannot remove that I suppose) - systems (`github:nix-systems/default`)