Use alejandra for formatting Nix files

flake.nix

@@ -1,18 +1,24 @@
 # Do not edit this file. It is automatically generated by https://www.oliverdavies.uk/build-configs.
-
 {
   inputs = {
     devshell.url = "github:numtide/devshell";
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
   };
 
-  outputs = inputs@{ flake-parts, ... }:
-    flake-parts.lib.mkFlake { inherit inputs; } {
-      imports = [ inputs.devshell.flakeModule ];
+  outputs = inputs @ {flake-parts, ...}:
+    flake-parts.lib.mkFlake {inherit inputs;} {
+      imports = [inputs.devshell.flakeModule];
 
-      systems = [ "x86_64-linux" ];
+      systems = ["x86_64-linux"];
 
-      perSystem = { config, self', inputs', pkgs, system, ... }: {
+      perSystem = {
+        config,
+        self',
+        inputs',
+        pkgs,
+        system,
+        ...
+      }: {
         devshells.default = {
           packages = with pkgs; [
             "nodePackages.pnpm"
@@ -21,6 +27,8 @@
             "php81Packages.composer"
           ];
         };
+
+        formatter = pkgs.alejandra;
       };
     };
 }