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/esnext.object.iterate-entries.js

@@ -0,0 +1,12 @@
+'use strict';
+// TODO: Remove from `core-js@4`
+var $ = require('../internals/export');
+var ObjectIterator = require('../internals/object-iterator');
+
+// `Object.iterateEntries` method
+// https://github.com/tc39/proposal-object-iteration
+$({ target: 'Object', stat: true, forced: true }, {
+  iterateEntries: function iterateEntries(object) {
+    return new ObjectIterator(object, 'entries');
+  }
+});