init flake with dev shell for node and cypress

flake.nix

@@ -0,0 +1,19 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "x86_64-linux";
+    in {
+      devShells."${system}".default = let
+        pkgs = import nixpkgs { inherit system; };
+      in pkgs.mkShell {
+        buildInputs = with pkgs; [
+          nodejs_25
+          cypress
+        ];
+      };
+    };
+}