Provide HTTP/2 server example in the website

[n1haldev]

Right now, hyper.rs only provides an HTTP/1 server example. It might be a good idea to add an HTTP/2 version.

This issue was raised in the hyper repository as hyperium/hyper#3568
Please assign this issue to me.

[dswij]

Let's keep the issues in one place in hyper for easier tracking. You can open up a PR (or draft) to this repo if you want to help with the website documentation.