Use an [AsyncWrite] as a [Sink]<Item: AsRef<[u8]>.

This adapter produces a sink that will write each value passed to it into the underlying writer. Note that this function consumes the given writer, returning a wrapped version.

```rust use tokiointosink::IntoSinkExt as _; use futures::{stream, StreamExt as _}; use std::io;

let stream = stream::iter(["hello", "world"]).map(io::Result::Ok); let write = tokio::fs::File::create("/dev/null").await.unwrap(); let sink = write.into_sink(); stream.forward(sink).await.unwrap(); ```

Ported from futures::io::AsyncWriteExt::into_sink.