HTTP3 support

[onionj]

Hi ❤
Any plan to support HTTP3?

[alexflint]

Yeah, I would very much like to. I need to look through the http3 package to figure out how to do transparent TLS termination. Other than that it should be fairly straightforward.

For my own reference later, here is where http3 requests are parsed and dispatched by the http3 package: https://github.com/quic-go/quic-go/blob/v0.50.0/http3/server.go#L592-L716