Support async generator based streaming API in javascript

[davidfowl]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

JavaScript supports async generators now and SignalR still only supports the RX based callback model:

https://learn.microsoft.com/en-us/aspnet/core/signalr/streaming?view=aspnetcore-9.0

Describe the solution you'd like

https://learn.microsoft.com/en-us/aspnet/core/signalr/streaming?view=aspnetcore-9.0#javascript-client

An API that looks like this:

var stream = await connection.streamAsync("Counter", 10, 500);

try
{
    for await (const value of stream)
    {
          var li = document.createElement("li");
          li.textContent = item;
          document.getElementById("messagesList").appendChild(li);
    }
}
catch(err)
{
    var li = document.createElement("li");
    li.textContent = err;
    document.getElementById("messagesList").appendChild(li);   
}

var li = document.createElement("li");
li.textContent = "Stream completed";
document.getElementById("messagesList").appendChild(li);

Additional context

No response

[davidfowl]

cc @BrennanConroy