itsybitsy_m0-0.1.0 doesn't have any documentation.
Adafruit ItsyBitsy M0 Board Support Crate
This crate provides a type-safe API for working with the Adafruit ItsyBitsy M0 board.
Examples?
Check out the repository for examples:
https://github.com/atsamd-rs/atsamd21-rs/tree/master/boards/itsybitsy_m0/examples