Improve toast accessibility

[skjnldsv]

Some suggestions:

1. State the type of message

Announcing the type first (like "Error: [message]"), this is generally a good practice:

• It immediately communicates the severity to screen reader users
• It helps users mentally prepare for the information
• It provides context similar to how visual users get from the colors/icons

<div aria-live="assertive" aria-atomic="true">
  <span class="visually-hidden">Error:</span>
  <p>Your form submission failed. Please try again.</p>
</div>

2. Use role="alert"

https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/alert_role
For stronger levels like error or warning, I think this fits the use case

[skjnldsv]

@ShGKme @susnux

[ShGKme]

Seems possible by wrapping toast methods to provide a custom node option.

[skjnldsv]

We can also improve the lib itself 😉

[susnux]

Or move away from it completely and implement our own NcToast for it^^