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/iframe-has-title.md

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+# jsx-a11y/iframe-has-title
+
+💼 This rule is enabled in the following configs: ☑️ `recommended`, 🔒 `strict`.
+
+<!-- end auto-generated rule header -->
+
+`<iframe>` elements must have a unique title property to indicate its content to the user.
+
+## Rule details
+
+This rule takes no arguments.
+
+### Succeed
+```jsx
+<iframe title="This is a unique title" />
+<iframe title={uniqueTitle} />
+```
+
+### Fail
+```jsx
+<iframe />
+<iframe {...props} />
+<iframe title="" />
+<iframe title={''} />
+<iframe title={``} />
+<iframe title={undefined} />
+<iframe title={false} />
+<iframe title={true} />
+<iframe title={42} />
+```
+
+## Accessibility guidelines
+- [WCAG 2.4.1](https://www.w3.org/WAI/WCAG21/Understanding/bypass-blocks)
+- [WCAG 4.1.2](https://www.w3.org/WAI/WCAG21/Understanding/name-role-value)
+
+### Resources
+- [axe-core, frame-title](https://dequeuniversity.com/rules/axe/3.2/frame-title)