Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/@humanwhocodes/module-importer/dist/module-importer.js

@@ -0,0 +1,18 @@
+import { createRequire } from 'module';
+import { fileURLToPath } from 'url';
+import { dirname } from 'path';
+
+/**
+ * @fileoverview Universal module importer
+ */
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+const require = createRequire(__dirname + "/");
+const { ModuleImporter } = require("./module-importer.cjs");
+
+export { ModuleImporter };