Improve replay banner's accessibility

[lwrubel]

Description

• Puts banner in header and nav landmark regions
• Adds landmark role of banner to header

Motivation and Context

The SiteImprove automated accessibility checker flags the replay banner for not following ARIA Authoring Practices, specifically concerning landmark regions. These changes are intended to improve site navigation by screen readers.

Types of changes

• Replay fix (fixes a replay specific issue)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added or updated tests to cover my changes.
• All new and existing tests passed.