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/nthArg.js

@@ -0,0 +1,32 @@
+var baseNth = require('./_baseNth'),
+    baseRest = require('./_baseRest'),
+    toInteger = require('./toInteger');
+
+/**
+ * Creates a function that gets the argument at index `n`. If `n` is negative,
+ * the nth argument from the end is returned.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.0.0
+ * @category Util
+ * @param {number} [n=0] The index of the argument to return.
+ * @returns {Function} Returns the new pass-thru function.
+ * @example
+ *
+ * var func = _.nthArg(1);
+ * func('a', 'b', 'c', 'd');
+ * // => 'b'
+ *
+ * var func = _.nthArg(-2);
+ * func('a', 'b', 'c', 'd');
+ * // => 'c'
+ */
+function nthArg(n) {
+  n = toInteger(n);
+  return baseRest(function(args) {
+    return baseNth(args, n);
+  });
+}
+
+module.exports = nthArg;