[idea] http/3 support sample

Provide a good sample how to enable http/3 support for clients written with help of mappersmith.

refs:
- https://en.wikipedia.org/wiki/HTTP/3
- https://github.com/nodejs/node/issues/38478
- https://medium.com/@queenskisivuli/webtransport-a-new-way-to-communicate-over-http-3-a730a8c84790\
- https://www.smashingmagazine.com/2021/09/http3-practical-deployment-options-part3/