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/core-js-pure/internals/is-regexp.js

@@ -0,0 +1,13 @@
+'use strict';
+var isObject = require('../internals/is-object');
+var classof = require('../internals/classof-raw');
+var wellKnownSymbol = require('../internals/well-known-symbol');
+
+var MATCH = wellKnownSymbol('match');
+
+// `IsRegExp` abstract operation
+// https://tc39.es/ecma262/#sec-isregexp
+module.exports = function (it) {
+  var isRegExp;
+  return isObject(it) && ((isRegExp = it[MATCH]) !== undefined ? !!isRegExp : classof(it) === 'RegExp');
+};