No way to proxy SSE data

[lsmenicucci]

It would be interesting if there was a way to update the server side event's data before they got swapped into the elements.

The main reason for this is that SSE specification uses \n\n as an event terminator and the way to send multiline data is to base64 encode it before. However, there is no way to decode it on the frontend before the swap. At least not to my knowledge.