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/modules/toPath.js

@@ -0,0 +1,9 @@
+import _ from './underscore.js';
+import isArray from './isArray.js';
+
+// Normalize a (deep) property `path` to array.
+// Like `_.iteratee`, this function can be customized.
+export default function toPath(path) {
+  return isArray(path) ? path : [path];
+}
+_.toPath = toPath;