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/internals/iterate-simple.js

@@ -0,0 +1,12 @@
+'use strict';
+var call = require('../internals/function-call');
+
+module.exports = function (record, fn, ITERATOR_INSTEAD_OF_RECORD) {
+  var iterator = ITERATOR_INSTEAD_OF_RECORD ? record : record.iterator;
+  var next = record.next;
+  var step, result;
+  while (!(step = call(next, iterator)).done) {
+    result = fn(step.value);
+    if (result !== undefined) return result;
+  }
+};