Add guidelines on how CBOR messages are mapped onto streams about openscreenprotocol

[mfoltzgoogle]

MAX_STREAMS is negotiated between peers as a transport parameter. We should just tell agents to set MAX_STREAMS to a limit that is high enough so that it does not limit the protocol in practice.

An application sending 1 message/ms and allowing retransmissions for 10 seconds would have 10,000 concurrent streams. We can just set a minimum MAX_STREAMS of 2^17 to provide additional headroom.

[mfoltzgoogle]

Correction: MAX_STREAMS limits the cumulative number of streams that can be opened per connection. For long lived connections, we will need a higher value. For a year-long connection, that could be as high as 400M according to the math above.