Add role="group" to transcript focusable

[compulim]

Fixes #3764.

Changelog Entry

Fixed

• Fixes #3764. Added role="group" to the focusable transcript to enable aria-activedescendant, by @compulim in PR #3765

Description

Add role="group" to transcript focusable element, to enable aria-activedescendant in macOS Safari + VoiceOver.

Design

According to WAI-ARIA, aria-activedescendant will only work with one of the following role:

• application
• composite with subclass of
  • grid
  • select
  • spinbutton
  • tablist
• group
• textbox
• combobox
• grid
• listbox
• menu
• menubar
• radiogroup
• row
• searchbox
• select
• spinbutton
• tablist
• toolbar
• tree
• treegrid

Specific Changes

• Add role="group" to the focusable of <BasicTranscript>

• 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)