edge-std-nal-async

A stop-gap STD implementation of embedded-nal-async, including the extra traits defined in embedded-nal-async-xtra.

The implementation is based on the minimalistic async-io crate - from the smol async echosystem - and thus works out of the box on a variety of operating systems, including Espressif's ESP IDF.

Plan Forward

Once the traits are upstreamed, the hope is that the "other" - and a bit more known - STD-based embedded-nal-async implementation - std-embedded-nal-async will implement those.

There is also an open PR against std-embedded-nal-async to remove its dependency on async-std and switch to async-io.