Add nix flake

.gitignore

@@ -2,3 +2,5 @@ bin
 releases
 extra/man/chrome-shell.1.gz
 extra/man/chrome-shell.1.html
+# symbolic link created by nix
+result

flake.nix

@@ -0,0 +1,64 @@
+{
+  description = "A native messaging host for executing shell commands.";
+
+  # Nixpkgs / NixOS version to use.
+  inputs.nixpkgs.url = "nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      # Generate a user-friendly version number.
+      version = "nightly-4";
+
+      # System types to support.
+      supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];
+
+      # Helper function to generate an attrset '{ x86_64-linux = f "x86_64-linux"; ... }'.
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+
+      # Nixpkgs instantiated for supported system types.
+      nixpkgsFor = forAllSystems (system: import nixpkgs { inherit system; });
+
+    in
+    {
+
+      # enable nix fmt
+      formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixpkgs-fmt;
+
+      # Provide some binary packages for selected system types.
+      packages = forAllSystems (system:
+        let
+          pkgs = nixpkgsFor.${system};
+        in
+        {
+          chrome-shell = pkgs.crystal.buildCrystalPackage {
+            pname = "chrome-shell";
+            inherit version;
+            src = ./.;
+            format = "shards";
+
+            # nix cannot run git commands to generate the version string,
+            # patch the sources to set the version string
+            patchPhase = ''
+              sed -i "s/{{.*}}/\"${version}\"/" src/main.cr
+            '';
+          };
+        });
+
+      # Add dependencies that are only needed for development
+      devShells = forAllSystems (system:
+        let
+          pkgs = nixpkgsFor.${system};
+        in
+        {
+          default = pkgs.mkShell {
+            buildInputs = (with pkgs; [ nixd ])
+              ++ (with self.packages.${system}.chrome-shell; nativeBuildInputs ++ buildInputs);
+          };
+        });
+
+      # The default package for 'nix build'. This makes sense if the
+      # flake provides only one package or there is a clear "main"
+      # package.
+      defaultPackage = forAllSystems (system: self.packages.${system}.chrome-shell);
+    };
+}