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-abstract/2023/KeyForSymbol.js

@@ -0,0 +1,16 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var callBound = require('call-bound');
+
+var $keyFor = callBound('Symbol.keyFor', true);
+
+// https://262.ecma-international.org/14.0/#sec-keyforsymbol
+
+module.exports = function KeyForSymbol(sym) {
+	if (typeof sym !== 'symbol') {
+		throw new $TypeError('Assertion failed: `sym` must be a Symbol');
+	}
+	return $keyFor(sym);
+};