[Todo] http: add support for extended connect protocol

[jasnell]

Now that RFC 8441 has been published detailing how to bootstrap Web Sockets support over HTTP/2, it will be necessary to enable support for the "Extended CONNECT protocol" as defined in the spec. This cannot be done in a third party module and has to be implemented directly by Node.js (and possibly nghttp2). I will be investigating this implementation soon but I wanted to leave a tracking issue to make folks aware.

/cc @nodejs/http2

[jasnell]

This will definitely require support in nghttp2 to land first: nghttp2/nghttp2#1181 (comment)

[jasnell]

This happened.