When entering edit mode, inform users through the aria-live aural update interface about the state of page

Problem/Motivation

When entering edit mode, without visual cues, the changed state of the page is not discernable. For example, the page is rendered in a "mode" that requires a user to save or exit the mode. The user is no longer consuming content, they are editing content. Users who navigate content aurally require information about the state of the page presented through sound rather than visuals.

Proposed resolution

Introduce an aria live region to the Edit module HTML output and a set of methods that allow updates to this region to be posted as the Edit module changes the state of the page.

Updates that should be noted

• Edit mode is active. The tab index has been altered.
• Controls to save and publish changes, as well as exit edit mode, are available.
• There are N number of editable fields on the page.
• A new editable field has been added to the page.
• The page content has been changed.
• Changes have been abandoned.

Aria live region documentation

https://developer.mozilla.org/en-US/docs/Accessibility/ARIA/ARIA_Live_Re...

Remaining tasks

Propose an initial patch.

User interface changes

For aural UI users, they will have additional information about changes to the page's state.

API changes

None.