Docs missing for http2Stream.id and the 'ready' event

[jakearchibald]

I wrote a piece of code that made a request to A, and after a moment, made a request to B with the prior stream as a parent.

This means I needed to pass the ID of stream A to the client.request call for stream B.

stream.id is mentioned in passing, but it isn't specifically documented.

Same goes for the ready event.

[Trott]

@nodejs/documentation @nodejs/http2

[ryzokuken]

I tried to do something like this in nodejs/help#877 (comment), but was stalled. Perhaps we could break these into a couple of "good second issue"s?

[ryzokuken]

/cc @mcollina

[mcollina]

stream.id is the HTTP2 Stream id.

ready is emitted when an id is available.