RESET_STREAM_AT is used, but not required

Fixes #874

Author: ianswett

draft-ietf-moq-transport.md

@@ -510,7 +510,10 @@ semantics (see {{?I-D.ietf-webtrans-overview, Section 4}}); thus, the
 main difference lies in how the servers are identified and how the
 connection is established.  When using QUIC, datagrams MUST be
 supported via the [QUIC-DATAGRAM] extension, which is already a
-requirement for WebTransport over HTTP/3.
+requirement for WebTransport over HTTP/3. The RESET_STREAM_AT
+{{!I-D.draft-ietf-quic-reliable-stream-reset}} extension to QUIC
+can be used by MoQT, but the protocol is also designed to work
+correctly when the extension is not supported.
 
 There is no definition of the protocol over other transports,
 such as TCP, and applications using MoQ might need to fallback to