Accessibility improvement: indicate table heading

[svenaas]

The published files table at /sites/[id]/published/[branch]) is missing a th or ARIA attribute property marking the header, which can prevent screen readers from semantically associating cells with the appropriate header.

Notes

• Reported in February 22, 2024 Section 508 Evaluation

Acceptance Criteria

• [ ] Add th or suitable ARIA property to the table