Intent to Implement: Serial API

We have a number of hardware devices that are programmable via the serial port, and this API would be a nice way to provide that functionality directly via the web.

Most programming cables we use are USB to serial devices, which would suggest we could use WebUSB, but WebUSB only works for devices that haven't been claimed by the operating system, and it requires writing a Javascript driver for the serial chipset used by the cable (although there are a number of open source ones that could be used with some modifications, eg: https://github.com/tidepool-org/pl2303).

The detailed serial API specification is available at: https://wicg.github.io/serial/