WebSocket or notification endpoint to update content in AMP Email that a user currently has open

### Description

Apologies if there's a way to do this, but it didn't look like it from the documentation.

What I would like to do is have a QR code in an email (probably an amp-img) where the src is loaded from a remote server. Then, when our system detects that the QR code has been scanned, it can send a notification or WebSocket push so that the amp-img source is replaced with a green check or other kind of indicator. This would help users have immediate feedback as to when their QR code has been scanned successfully.

### Alternatives Considered

Without being able to live update content in response to a notification, we'd probably just have to link out to a website from the email content (where we could then use React to replace the content in response to the WebSocket notification).

### Additional Context

_No response_