Add nix flake

flake.nix

@@ -0,0 +1,34 @@
+{
+    description = "ucg a configuration language compiler";
+
+    inputs = {
+        nixpkgs.url = "github:NixOS/nixpkgs";
+        flake-utils.url = "github:numtide/flake-utils";
+        rust-overlay = {
+            url = "github:oxalica/rust-overlay";
+            inputs.nixpkgs.follows = "nixpkgs";
+        };
+        naersk.url = "github:nix-community/naersk";
+        flake-compat = {
+            url = github:edolstra/flake-compat;
+            flake = false;
+        };
+    };
+
+    outputs = {self, nixpkgs, flake-utils, rust-overlay, naersk, flake-compat}:
+    flake-utils.lib.eachDefaultSystem (system:
+    let
+        overlays = [ rust-overlay.overlay ];
+        pkgs = import nixpkgs { inherit system overlays; };
+        naersk-lib = naersk.lib."${system}";
+    in
+    {
+        defaultPackage = with pkgs;
+            naersk-lib.buildPackage rec {
+                pname = "ucg";
+                version = "0.7.2";
+                src = ./.;
+                cargoBuildOptions = opts: opts ++ ["-p" "${pname}" ];
+            };
+    });
+}