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/_setCacheHas.js

@@ -0,0 +1,14 @@
+/**
+ * Checks if `value` is in the array cache.
+ *
+ * @private
+ * @name has
+ * @memberOf SetCache
+ * @param {*} value The value to search for.
+ * @returns {number} Returns `true` if `value` is found, else `false`.
+ */
+function setCacheHas(value) {
+  return this.__data__.has(value);
+}
+
+module.exports = setCacheHas;