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-import/config/react.js

@@ -0,0 +1,16 @@
+/**
+ * Adds `.jsx` as an extension, and enables JSX parsing.
+ *
+ * Even if _you_ aren't using JSX (or .jsx) directly, if your dependencies
+ * define jsnext:main and have JSX internally, you may run into problems
+ * if you don't enable these settings at the top level.
+ */
+module.exports = {
+  settings: {
+    'import/extensions': ['.js', '.jsx'],
+  },
+
+  parserOptions: {
+    ecmaFeatures: { jsx: true },
+  },
+};