Add Nix Flake with nodejs and just

.envrc

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+use flake .

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1711523803,
+        "narHash": "sha256-UKcYiHWHQynzj6CN/vTcix4yd1eCu1uFdsuarupdCQQ=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "2726f127c15a4cc9810843b96cad73c7eb39e443",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "An example application that uses Stimulus with esbuild.";
+
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+  outputs = { nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      inherit (pkgs) mkShell;
+    in {
+      devShells.${system}.default = mkShell {
+        buildInputs = with pkgs; [ just nodejs simple-http-server ];
+      };
+
+      formatter.${system} = pkgs.nixfmt;
+    };
+}