chore: add flake

flake.nix

@@ -0,0 +1,35 @@
+{
+  description = "Ephemeral Nix Environment";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs, ... }:
+    let
+      system = if builtins.currentSystem == "x86_64-darwin" then "x86_64-darwin"
+                else if builtins.currentSystem == "aarch64-darwin" then "aarch64-darwin"
+                else "x86_64-linux";
+    in
+    {
+      devShells."${system}".default =
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+          };
+        in
+        pkgs.mkShell {
+          # create an environment with nodejs_20, and pnpm
+          packages = with pkgs; [
+            nodejs_20
+            nodePackages.pnpm
+            nushell # BECAUSE I WANT NUSHELL
+          ];
+
+          shellHook = ''
+            echo "node `${pkgs.nodejs}/bin/node --version`"
+            exec nu
+          '';
+        };
+    };
+}