Add Nix flake examples

nix/flakes/simple/.envrc

@@ -0,0 +1 @@
+use flake

nix/flakes/simple/flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1754214453,
+        "narHash": "sha256-Q/I2xJn/j1wpkGhWkQnm20nShYnG7TI99foDBpXm1SY=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "5b09dc45f24cf32316283e62aec81ffee3c3e376",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

nix/flakes/simple/flake.nix

@@ -0,0 +1,20 @@
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+  outputs =
+    inputs:
+    let
+      system = "x86_64-linux";
+      pkgs = import inputs.nixpkgs { inherit system; };
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        packages = with pkgs; [
+          go
+          php
+          phpPackages.composer
+          tailwindcss
+        ];
+      };
+    };
+}