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-jsx-a11y/docs/rules/scope.md

@@ -0,0 +1,30 @@
+# jsx-a11y/scope
+
+💼 This rule is enabled in the following configs: ☑️ `recommended`, 🔒 `strict`.
+
+<!-- end auto-generated rule header -->
+
+The `scope` prop should be used only on `<th>` elements.
+
+## Rule details
+
+This rule takes no arguments.
+
+### Succeed
+```jsx
+<th scope="col" />
+<th scope={scope} />
+```
+
+### Fail
+
+```jsx
+<div scope />
+```
+
+## Accessibility guidelines
+- [WCAG 1.3.1](https://www.w3.org/WAI/WCAG21/Understanding/info-and-relationships)
+- [WCAG 4.1.1](https://www.w3.org/WAI/WCAG21/Understanding/parsing)
+
+### Resources
+- [axe-core, scope-attr-valid](https://dequeuniversity.com/rules/axe/3.5/scope-attr-valid)