Add shell.nix with hugo

.envrc

@@ -0,0 +1 @@
+use_nix

shell.nix

@@ -0,0 +1,10 @@
+let
+  channel = "nixos-23.11";
+  pkgs = import <nixpkgs> { };
+in
+pkgs.mkShell {
+  name = "hugo site";
+  buildInputs = [
+    pkgs.hugo
+  ];
+}