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/node/CDC.js

@@ -0,0 +1,19 @@
+var CDC = require('../../tokenizer').TYPE.CDC;
+
+module.exports = {
+    name: 'CDC',
+    structure: [],
+    parse: function() {
+        var start = this.scanner.tokenStart;
+
+        this.eat(CDC); // -->
+
+        return {
+            type: 'CDC',
+            loc: this.getLocation(start, this.scanner.tokenStart)
+        };
+    },
+    generate: function() {
+        this.chunk('-->');
+    }
+};