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/eslint-plugin-react/lib/util/getTokenBeforeClosingBracket.js

@@ -0,0 +1,16 @@
+'use strict';
+
+/**
+ * Find the token before the closing bracket.
+ * @param {ASTNode} node - The JSX element node.
+ * @returns {Token} The token before the closing bracket.
+ */
+function getTokenBeforeClosingBracket(node) {
+  const attributes = node.attributes;
+  if (!attributes || attributes.length === 0) {
+    return node.name;
+  }
+  return attributes[attributes.length - 1];
+}
+
+module.exports = getTokenBeforeClosingBracket;