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/@pkgjs/parseargs/internal/util.js

@@ -0,0 +1,14 @@
+'use strict';
+
+// This is a placeholder for util.js in node.js land.
+
+const {
+  ObjectCreate,
+  ObjectFreeze,
+} = require('./primordials');
+
+const kEmptyObject = ObjectFreeze(ObjectCreate(null));
+
+module.exports = {
+  kEmptyObject,
+};