Looks great, thanks for sharing!
How does it compare to the February 2020 standard draft from IETF? [1] I was following the development of the Websocket protocol pretty closely when it happened and had to update my implementation[2] multiple times as the design kept changing. Did this also happen here, or was QUIC pretty much done and standardized straight from the Google design?
[1] https://tools.ietf.org/html/draft-ietf-quic-transport-27