No way to determine if the server reset the stream

[bruceg]

When a server (GCP Pub/Sub in my case) sends a reset frame, h2 reports it as a status with Kind::Reset. However, there is no direct way of testing if the status was a reset, analogous to is_go_away or is_io.

If an is_reset function would be an acceptable solution, I can provide a PR for this.

[seanmonstar]

Yea that's probably just an oversight, I can't think of any reason it wouldn't exist.