Add Nix flake examples

nix/flakes/flake-parts/flake.nix

@@ -0,0 +1,31 @@
+{
+  inputs = {
+    devshell.inputs.nixpkgs.follows = "nixpkgs";
+    devshell.url = "github:numtide/devshell";
+
+    flake-parts.url = "github:hercules-ci/flake-parts";
+
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs =
+    inputs:
+    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+      systems = [ "x86_64-linux" ];
+
+      imports = [ inputs.devshell.flakeModule ];
+
+      perSystem =
+        { pkgs, ... }:
+        {
+          devshells.default = {
+            packages = with pkgs; [
+              go
+              php
+              phpPackages.composer
+              tailwindcss
+            ];
+          };
+        };
+    };
+}