A new multi-threaded `hello-world` example for `cargo-wasix`

[dynamite-bud]

Motivation

The current hello-world program is too simple, and just shows the basic compilation of a rust based program. If users are already well versed to enter this ecosystem. Then we should have another entry hello-world program.

Example

Hello world with a multithreaded API with JSON responses. This was suggested by a user from hn.