[Accessibility] Narrate AC/attachments by reading their `innerText`

[compulim]

Is your feature request related to a problem?

Chromium browser is buggy at narrating complex contents. That's why Web Chat disabled narration of Adaptive Cards.

Describe the suggestion or request in detail

Read AC innerText and narrate that part. This would workaround browser bug.

Describe alternatives you have considered

"Click to interact" prompt is not popular.

Narration cutoff is not desirable.

Additional context

No response