fix issue#33025 (docs): add visible focus outline for keyboard navigation in Docs …

[Kamalllx]

Closes #33025

What I did

Added visible :focus-visible styles for interactive elements (links, buttons, inputs, textareas, and selects) within the Docs view to ensure keyboard focus indicators are visible when navigating with Tab/Shift+Tab.

Changes:

• Added a new style rule in DocsPage.tsx that applies a 2px solid outline using the theme's secondary color to all interactive elements when focused via keyboard
• Included outline-offset: 2px for better visual separation
• Added fallback support for high-contrast/forced-colors environments using @media (forced-colors: active)

This fix improves accessibility compliance with WCAG 2.1.1 (Keyboard) and WCAG 2.4.7 (Focus Visible).

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

1. Run a sandbox: yarn task --task sandbox --start-from auto --template react-vite/default-ts
2. Open Storybook in your browser at http://localhost:6006
3. Navigate to any story's Docs view
4. Use the Tab key to navigate between interactive elements (links, buttons, "Show code", "Copy" buttons)
5. Verify that each focused element displays a visible outline (2px solid border)
6. Test with both light and dark themes

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD