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/espree/lib/features.js

@@ -0,0 +1,27 @@
+/**
+ * @fileoverview The list of feature flags supported by the parser and their default
+ *      settings.
+ * @author Nicholas C. Zakas
+ */
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+// None!
+
+//------------------------------------------------------------------------------
+// Public
+//------------------------------------------------------------------------------
+
+export default {
+
+    // React JSX parsing
+    jsx: false,
+
+    // allow return statement in global scope
+    globalReturn: false,
+
+    // allow implied strict mode
+    impliedStrict: false
+};