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/2024/ToZeroPaddedDecimalString.js

@@ -0,0 +1,19 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $String = GetIntrinsic('%String%');
+var $RangeError = require('es-errors/range');
+var isInteger = require('math-intrinsics/isInteger');
+
+var StringPad = require('./StringPad');
+
+// https://262.ecma-international.org/13.0/#sec-tozeropaddeddecimalstring
+
+module.exports = function ToZeroPaddedDecimalString(n, minLength) {
+	if (!isInteger(n) || n < 0) {
+		throw new $RangeError('Assertion failed: `q` must be a non-negative integer');
+	}
+	var S = $String(n);
+	return StringPad(S, minLength, '0', 'start');
+};