docs(server): add bigger example to server module (#2539)
docs(server): add bigger example to server module (#2539)

It can sometimes be tricky to discover where to use `move` closures,
`async move {}`, and `.clone()` when creating a server. This adds a
slightly more bigger example that will hopefully help some.

Fixes https://github.com/hyperium/hyper/issues/2446
tshepang/hyper,tshepang/hyper,tshepang/hyper,hyperium/hyper,hyperium/hyper,hyperium/hyper