HTTP/2 support

[ipkn]

HTTP/2 support is needed.

[digitalist]

https://nghttp2.org/documentation/libnghttp2_asio.html
this framework have something in common with crow, routing for example.
maybe cooperation is possible

[moneroexamples]

@digitalist

Do you know what are differences between crow and libnghttp2_asio? Specifically, did you try porting crow into libnghttp2_asio and got into major problems?