fix: allow focusing code block contents

[OEvgeny]

Fixes #

Changelog Entry

• Fixed placing focus on the code block content, so it is possible to scroll code via keyboard, in PR #5575, by @OEvgeny

Description

This fixes the scroll behavior of code blocks as well as detection of non-focusable elements, so it's harder to escape from our FocusTrap component.

This also migrates related code block styles to CSSModules.

Specific Changes

• *.module.css, *.tsx - migrated styles to CSSModules
• tabbableElements.ts - updated implementation to include detect non focusable element via styles
• viewCodeButton.scroll.html - test to verify scrolling code block works

-

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[compulim]

Let's do it!