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/_flatRest.js

@@ -0,0 +1,16 @@
+var flatten = require('./flatten'),
+    overRest = require('./_overRest'),
+    setToString = require('./_setToString');
+
+/**
+ * A specialized version of `baseRest` which flattens the rest array.
+ *
+ * @private
+ * @param {Function} func The function to apply a rest parameter to.
+ * @returns {Function} Returns the new function.
+ */
+function flatRest(func) {
+  return setToString(overRest(func, undefined, flatten), func + '');
+}
+
+module.exports = flatRest;