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/@jest/globals/build/index.js

@@ -0,0 +1,25 @@
+'use strict';
+
+function _expect() {
+  const data = _interopRequireDefault(require('expect'));
+
+  _expect = function () {
+    return data;
+  };
+
+  return data;
+}
+
+function _interopRequireDefault(obj) {
+  return obj && obj.__esModule ? obj : {default: obj};
+}
+
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+throw new Error(
+  'Do not import `@jest/globals` outside of the Jest test environment'
+);