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/cjs/indexOf.js

@@ -0,0 +1,11 @@
+var _createIndexFinder = require('./_createIndexFinder.js');
+var sortedIndex = require('./sortedIndex.js');
+var findIndex = require('./findIndex.js');
+
+// Return the position of the first occurrence of an item in an array,
+// or -1 if the item is not included in the array.
+// If the array is large and already in sort order, pass `true`
+// for **isSorted** to use binary search.
+var indexOf = _createIndexFinder(1, findIndex, sortedIndex);
+
+module.exports = indexOf;