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/IdSelector.js

@@ -0,0 +1,27 @@
+var TYPE = require('../../tokenizer').TYPE;
+
+var HASH = TYPE.Hash;
+
+// <hash-token>
+module.exports = {
+    name: 'IdSelector',
+    structure: {
+        name: String
+    },
+    parse: function() {
+        var start = this.scanner.tokenStart;
+
+        // TODO: check value is an ident
+        this.eat(HASH);
+
+        return {
+            type: 'IdSelector',
+            loc: this.getLocation(start, this.scanner.tokenStart),
+            name: this.scanner.substrToCursor(start + 1)
+        };
+    },
+    generate: function(node) {
+        this.chunk('#');
+        this.chunk(node.name);
+    }
+};