Fixes #2996.

Changelog Entry

Added

• Resolves #2996. Added transcript navigation by keyboard navigation keys, by @compulim in PR #3703

Description

When focused in the transcript, pressing UP, DOWN, HOME, END should activate different activities (via aria-activedescendant).

When focused in the send box, pressing PGUP, PGDN, HOME, END should scroll the transcript.

If "New messages" button appears, clicking on it should activate the next unread activity.

Design

(TBD)

Specific Changes

(TBD)

• 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)