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/modules/web.dom-collections.iterator.js

@@ -0,0 +1,11 @@
+'use strict';
+require('../modules/es.array.iterator');
+var DOMIterables = require('../internals/dom-iterables');
+var globalThis = require('../internals/global-this');
+var setToStringTag = require('../internals/set-to-string-tag');
+var Iterators = require('../internals/iterators');
+
+for (var COLLECTION_NAME in DOMIterables) {
+  setToStringTag(globalThis[COLLECTION_NAME], COLLECTION_NAME);
+  Iterators[COLLECTION_NAME] = Iterators.Array;
+}