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/iterator-close.js

@@ -0,0 +1,24 @@
+'use strict';
+var call = require('../internals/function-call');
+var anObject = require('../internals/an-object');
+var getMethod = require('../internals/get-method');
+
+module.exports = function (iterator, kind, value) {
+  var innerResult, innerError;
+  anObject(iterator);
+  try {
+    innerResult = getMethod(iterator, 'return');
+    if (!innerResult) {
+      if (kind === 'throw') throw value;
+      return value;
+    }
+    innerResult = call(innerResult, iterator);
+  } catch (error) {
+    innerError = true;
+    innerResult = error;
+  }
+  if (kind === 'throw') throw value;
+  if (innerError) throw innerResult;
+  anObject(innerResult);
+  return value;
+};