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/es-define-property/index.js

@@ -0,0 +1,14 @@
+'use strict';
+
+/** @type {import('.')} */
+var $defineProperty = Object.defineProperty || false;
+if ($defineProperty) {
+	try {
+		$defineProperty({}, 'a', { value: 1 });
+	} catch (e) {
+		// IE 8 has a broken defineProperty
+		$defineProperty = false;
+	}
+}
+
+module.exports = $defineProperty;