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/lib/shared/directives.js

@@ -0,0 +1,15 @@
+/**
+ * @fileoverview Common utils for directives.
+ *
+ * This file contains only shared items for directives.
+ * If you make a utility for rules, please see `../rules/utils/ast-utils.js`.
+ *
+ * @author gfyoung <https://github.com/gfyoung>
+ */
+"use strict";
+
+const directivesPattern = /^(eslint(?:-env|-enable|-disable(?:(?:-next)?-line)?)?|exported|globals?)(?:\s|$)/u;
+
+module.exports = {
+    directivesPattern
+};