[terra-clinical-data-grid] Add accessibility for empty cells

[sbulley09]

Feature Request

Description

Selectable data grid cells which do not have content currently get flagged for accessibility violations. Since empty cells are common, we would like a method by which we can be compliant with the accessibility standard. Perhaps an aria-label option in the cells properties.

Additional Context / Screenshots

This screenshot displays a scenario where there is no text in a cell, but they violate the accessibility rules.

@ Mentions

I've spoken briefly with @tbiethman about this enhancement.