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/MediaQueryList.js

@@ -0,0 +1,36 @@
+var COMMA = require('../../tokenizer').TYPE.Comma;
+
+module.exports = {
+    name: 'MediaQueryList',
+    structure: {
+        children: [[
+            'MediaQuery'
+        ]]
+    },
+    parse: function(relative) {
+        var children = this.createList();
+
+        this.scanner.skipSC();
+
+        while (!this.scanner.eof) {
+            children.push(this.MediaQuery(relative));
+
+            if (this.scanner.tokenType !== COMMA) {
+                break;
+            }
+
+            this.scanner.next();
+        }
+
+        return {
+            type: 'MediaQueryList',
+            loc: this.getLocationFromList(children),
+            children: children
+        };
+    },
+    generate: function(node) {
+        this.children(node, function() {
+            this.chunk(',');
+        });
+    }
+};