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/2022/StringIndexOf.js

@@ -0,0 +1,36 @@
+'use strict';
+
+var callBound = require('call-bound');
+
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+
+var $slice = callBound('String.prototype.slice');
+
+// https://262.ecma-international.org/12.0/#sec-stringindexof
+
+module.exports = function StringIndexOf(string, searchValue, fromIndex) {
+	if (typeof string !== 'string') {
+		throw new $TypeError('Assertion failed: `string` must be a String');
+	}
+	if (typeof searchValue !== 'string') {
+		throw new $TypeError('Assertion failed: `searchValue` must be a String');
+	}
+	if (!isInteger(fromIndex) || fromIndex < 0) {
+		throw new $TypeError('Assertion failed: `fromIndex` must be a non-negative integer');
+	}
+
+	var len = string.length;
+	if (searchValue === '' && fromIndex <= len) {
+		return fromIndex;
+	}
+
+	var searchLen = searchValue.length;
+	for (var i = fromIndex; i <= (len - searchLen); i += 1) {
+		var candidate = $slice(string, i, i + searchLen);
+		if (candidate === searchValue) {
+			return i;
+		}
+	}
+	return -1;
+};