C++ coroutine with epoll

Use C++20 coroutine to have async accept / recv / send operation

Exemple echo server with in the main.cc

Purpose

Learning coroutine.

Inspired by:

• https://github.com/lewissbaker/cppcoro

TODO / Improvement

• catch sigint + destroy coroutine
• move semantic on socket accept (RVO ?)
• handling error
• clean (remove logging, ...)