Support acting as a Peripheral

[chrisballinger]

I know this is primarily intended to support the features of Web Bluetooth, but it would be great if we could use this wrapper to act as a peripheral as well.

[qdot]

It came out after this was posted, but now there's bluster for bluetooth peripherals, which is tokio async based and supports linux, mac, and possibly windows: https://github.com/dfrankland/bluster/