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/@babel/runtime/helpers/esm/defaults.js

@@ -0,0 +1,9 @@
+function _defaults(e, r) {
+  for (var t = Object.getOwnPropertyNames(r), o = 0; o < t.length; o++) {
+    var n = t[o],
+      a = Object.getOwnPropertyDescriptor(r, n);
+    a && a.configurable && void 0 === e[n] && Object.defineProperty(e, n, a);
+  }
+  return e;
+}
+export { _defaults as default };