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/istanbul-lib-report/lib/watermarks.js

@@ -0,0 +1,15 @@
+'use strict';
+/*
+ Copyright 2012-2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+module.exports = {
+    getDefault() {
+        return {
+            statements: [50, 80],
+            functions: [50, 80],
+            branches: [50, 80],
+            lines: [50, 80]
+        };
+    }
+};