build: add shell.nix

shell.nix

@@ -0,0 +1,13 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  unstable = import (builtins.fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz";
+  }) {};
+in
+pkgs.mkShell {
+  buildInputs = [
+    unstable.zig
+    pkgs.pciutils
+  ];
+}