feat: add nix flake (#631)

flake.nix

@@ -0,0 +1,29 @@
+{
+  description = "Minimal example of building Kotlin with Gradle and Nix";
+
+  inputs = {nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";};
+
+  inputs.systems.url = "github:nix-systems/default";
+
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs.flake-utils.inputs.systems.follows = "systems";
+
+  outputs = {
+    nixpkgs,
+    flake-utils,
+    ...
+  }:
+    flake-utils.lib.eachDefaultSystem (system: let
+      pkgs = import nixpkgs {inherit system;};
+      updateLocks = pkgs.callPackage ./update-locks.nix {};
+    in {
+      devShells.default = pkgs.mkShell {
+        buildInputs = with pkgs; [
+          gradle_8
+          temurin-bin-21
+          updateLocks
+          ktlint
+        ];
+      };
+    });
+}