add basic deno flake

flake.nix

@@ -0,0 +1,56 @@
+{
+  description = "Deno development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        toDenoTarget = system:
+          let
+            arch = builtins.head (builtins.split "-" system);
+            os = builtins.elemAt (builtins.split "-" system) 1;
+            vendor = if os == "darwin" then "apple" else "unknown";
+            sys = if os == "darwin" then "darwin" else "linux-gnu";
+          in "${arch}-${vendor}-${sys}";
+
+        target = toDenoTarget system;
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            deno
+          ];
+
+          shellHook = ''
+            echo "🦕 Deno development environment loaded!"
+            echo "Deno version: $(deno --version | head -n1)"
+          '';
+
+          DENO_DIR = "./.deno_cache";
+        };
+
+        # unfortunately this derivation is impure because
+        # managing deno's deps is HARD, so
+        # nix build --option sanbox relaxed
+        packages.default = import ./package.nix {
+          inherit pkgs;
+          inherit target;
+
+          name = "test-grimu-r-deno-app";
+        };
+
+        apps.default = {
+          type = "app";
+          program = toString (pkgs.writeShellScript "run-deno-app" ''
+            export DENO_DIR="./.deno_cache"
+            exec ${pkgs.deno}/bin/deno run main.ts "$@"
+          '');
+        };
+
+      });
+}