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/css-tree/lib/syntax/pseudo/index.js

@@ -0,0 +1,12 @@
+module.exports = {
+    'dir': require('./dir'),
+    'has': require('./has'),
+    'lang': require('./lang'),
+    'matches': require('./matches'),
+    'not': require('./not'),
+    'nth-child': require('./nth-child'),
+    'nth-last-child': require('./nth-last-child'),
+    'nth-last-of-type': require('./nth-last-of-type'),
+    'nth-of-type': require('./nth-of-type'),
+    'slotted': require('./slotted')
+};