[Pref] Upgrade site sever to HTTP/2

[Kimi-Gao]

HTTP/2 and Node.js

As of right now, there are two main implementations of HTTP/2 for Node.js:

• http2
• spdy

Both of them are very similar to the core http and https modules meaning if you don’t use Express, there’s very little difference. However, the spdy library supports HTTP/2 and Express while the http2 library is not supporting Express at this moment.

Express5 is a little difficult to be released, the last release was 5.0.0-alpha.7(Oct 27, 2018)

expressjs/express#2237

Reference

https://www.w3ctech.com/topic/2032
https://segmentfault.com/a/1190000009084692