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/underscore/amd/index-default.js

@@ -0,0 +1,12 @@
+define(['./mixin', './index'], function (mixin, index) {
+
+	// Default Export
+
+	// Add all of the Underscore functions to the wrapper object.
+	var _ = mixin(index);
+	// Legacy Node.js API.
+	_._ = _;
+
+	return _;
+
+});