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/object.groupby/shim.js

@@ -0,0 +1,17 @@
+'use strict';
+
+var define = require('define-properties');
+
+var getPolyfill = require('./polyfill');
+
+module.exports = function shim() {
+	var polyfill = getPolyfill();
+
+	define(
+		Object,
+		{ groupBy: polyfill },
+		{ groupBy: function () { return Object.groupBy !== polyfill; } }
+	);
+
+	return polyfill;
+};