Rust APIs and abstractions for embedded services

This crate ships traits for embedded features such as wifi, networking, httpd, logging. The intended use is for concrete implementations to use the traits provided in this crate as a common base. This would eventually lead to a portable embedded ecosystem. The APIs currently have a single implementation for the ESP32[-XX] / ESP-IDF. However, they are meant to be portable and should be possible to implement for other boards too.

For more information, check out: * The Rust on ESP Book * The esp-idf-svc project * The esp-idf-template project * The esp-idf-sys project * The esp-idf-hal project * The Rust for Xtensa toolchain * The Rust-with-STD demo project