Add content to empty table header cell to improve accessibility

[EWashb]

Background

Still an issue in D10

During an accessibility audit, it was found that the lack of cell header within the main content table is a 508 compliance defect.

Image of defective area:

Accessibility Standard

WCAG version 2.0 A, Criterion 1.3.1

Acceptance Criteria

• UX writes label for empty cell
• dev implementation of label
• accessibility review

[swirtSJW]

Some related discussion and options here #9823