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-shim-unscopables/index.js

@@ -0,0 +1,22 @@
+'use strict';
+
+var hasOwn = require('hasown');
+
+var hasUnscopables = typeof Symbol === 'function' && typeof Symbol.unscopables === 'symbol';
+
+var map = hasUnscopables && Array.prototype[Symbol.unscopables];
+
+var $TypeError = TypeError;
+
+/** @type {import('.')} */
+module.exports = function shimUnscopables(method) {
+	if (typeof method !== 'string' || !method) {
+		throw new $TypeError('method must be a non-empty string');
+	}
+	if (!hasOwn(Array.prototype, method)) {
+		throw new $TypeError('method must be on Array.prototype');
+	}
+	if (hasUnscopables && map) {
+		map[method] = true;
+	}
+};