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/_strictLastIndexOf.js

@@ -0,0 +1,21 @@
+/**
+ * A specialized version of `_.lastIndexOf` which performs strict equality
+ * comparisons of values, i.e. `===`.
+ *
+ * @private
+ * @param {Array} array The array to inspect.
+ * @param {*} value The value to search for.
+ * @param {number} fromIndex The index to search from.
+ * @returns {number} Returns the index of the matched value, else `-1`.
+ */
+function strictLastIndexOf(array, value, fromIndex) {
+  var index = fromIndex + 1;
+  while (index--) {
+    if (array[index] === value) {
+      return index;
+    }
+  }
+  return index;
+}
+
+module.exports = strictLastIndexOf;