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/2020/NumberToBigInt.js

@@ -0,0 +1,24 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $BigInt = GetIntrinsic('%BigInt%', true);
+var $RangeError = require('es-errors/range');
+var $SyntaxError = require('es-errors/syntax');
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+
+// https://262.ecma-international.org/11.0/#sec-numbertobigint
+
+module.exports = function NumberToBigInt(number) {
+	if (typeof number !== 'number') {
+		throw new $TypeError('Assertion failed: `number` must be a String');
+	}
+	if (!isInteger(number)) {
+		throw new $RangeError('The number ' + number + ' cannot be converted to a BigInt because it is not an integer');
+	}
+	if (!$BigInt) {
+		throw new $SyntaxError('BigInts are not supported in this environment');
+	}
+	return $BigInt(number);
+};