aria-description in popovers

[gwyneplaine]

Presently aria-description is used to give additional usage context for popover dialogs in the ListPage.
This is an ARIA 1.3 spec inclusion https://w3c.github.io/aria/#aria-description, so browser support is only at around 71%.
This manifests itself not only in React console errors, but also the descriptive text not being read out in unsupported browsers. https://caniuse.com/?search=aria-description

Ideally we should either have a more universally supported solution (aria-describedby or visually hidden element), or fallback to one if the attribute is not supported.