Add Nix flake configuration

flake.nix

@@ -0,0 +1,46 @@
+{
+  description = "NixOS/Darwin system configuration";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-22.11";
+    home-manager = {
+      url = "github:nix-community/home-manager/release-22.11";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = inputs @ { nixpkgs, home-manager, ... }:
+    let
+      inherit (lib) attrValues;
+      inherit (lib.my) mapModules mapModulesRec;
+
+      mkPkgs = pkgs:
+        import pkgs {
+          config.allowUnfree = true;
+        };
+      pkgs = mkPkgs nixpkgs;
+
+      lib = nixpkgs.lib.extend (self: super: {
+        my = import ./lib {
+          inherit pkgs inputs;
+          lib = self;
+        };
+      });
+    in {
+      lib = lib.my;
+
+      nixosModules = mapModulesRec ./modules import;
+
+      nixosConfigurations = {
+        atlas = nixpkgs.lib.nixosSystem {
+          system = "x86_64-linux";
+          modules = [
+            inputs.home-manager.nixosModules.home-manager
+            (import ./modules)
+            ./hosts/atlas
+          ];
+          specialArgs = { inherit lib inputs; };
+        };
+      };
+  };
+}