Proper Nix'ification

[orzklv]

The current development toolchain looks like this:

devShells.default = pkgs.mkShell ({
    buildInputs = with pkgs; [
      zlib
    ];
  });

Yes, at the moment this may not be significant, but when the bot will reach early deployment stage, all toolings with exact same working version of compiler, bla bla, including packaging stage (default.nix) should be clearly defined (especially if we are going to deploy it at Kolyma's DC). Therefore, I guess we should earlier sort it out and write proper shell.nix & default.nix to avoid further headaches.

[lambdajon]

@thelissimus Can we upgrade to version GHC 9.10.x?

[thelissimus]

@lambdajon Sure.