Similarly to messages with XWIKI-22168, xnotifications should have an `alert` ARIA role. This way, they are used by assistive techs. Typically, when a xnotification pops up, thanks to this role it will be read out immediately by screen readers.
Check out https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/alert_role and https://www.w3.org/WAI/ARIA/apg/patterns/alert/examples/alert/ to get examples of why this is useful.
