Add ThemeToggle component

flake.nix

@@ -0,0 +1,31 @@
+{
+  description = "JavaScript development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      # Systems supported
+      allSystems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+      
+      forAllSystems = f: nixpkgs.lib.genAttrs allSystems (system: f {
+        pkgs = nixpkgs.legacyPackages.${system};
+      });
+    in
+    {
+      devShells = forAllSystems ({ pkgs }: {
+        default = pkgs.mkShell {
+          packages = with pkgs; [
+            nodejs # Node.js, plus npm, npx, and corepack
+          ];
+        };
+      });
+    };
+}