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/lodash/stubFalse.js

@@ -0,0 +1,18 @@
+/**
+ * This method returns `false`.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.13.0
+ * @category Util
+ * @returns {boolean} Returns `false`.
+ * @example
+ *
+ * _.times(2, _.stubFalse);
+ * // => [false, false]
+ */
+function stubFalse() {
+  return false;
+}
+
+module.exports = stubFalse;