Add support for Async (non-blocking) Output Panel and Pop-up / Reply

[jasonjmcghee]

Integrating with existing apps is huge and super important - but often you want to be able to kick something off and come back (any kind of long running processes).

I think there should be a dedicated place that can take output in this way. (as opposed to writing in place, etc.)

And it should be only open when you want/need it.

I think pop-ups due to a trigger should be a thing. And we should consider specialized views, such as message / reply, and i'm sure many more.