Update docs and flake

[deemp]

Previously: part of #288

• Update docs
  • Refactor files structure
  • Add TOC
• Update flake
  • Update nixpkgs
  • Use flake-utils
  • Refactor to use flake-utils

[zimbatm]

thanks!

[sigprof]

Before this change it was possible to use the devshell flake without overlays (#162, #165):

    devshell.inputs.nixpkgs.follows = "nixpkgs";

          devShells.default = inputs.devshell.legacyPackages.${system}.mkShell {
            # ... configuration ...
          };

But this PR removed legacyPackages. What would be the proper way to use the devshell flake without overlays now?

The following works, but looks like a hack due to the non-flake import (and the inputs and nixpkgs arguments for default.nix don't seem to be documented):

          devshell = import inputs.devshell {
            inherit system;
            inputs = null;
            nixpkgs = inputs.nixpkgs.legacyPackages.${system};
          };

          devShells.default = devshell.mkShell {
            # ... configuration ...
          };

Is migrating to flake-parts the only supported way forward?

[deemp]

Thank you! It's a regression. The only way is to restore legacyPackages. I'll make a PR