Add switch-hal

Author: chrysn

README.md

@@ -700,6 +700,8 @@ devices which go beyond what is available in [`embedded-hal`]:
 - [`atat`](https://github.com/BlackbirdHQ/atat): Abstraction crate to ease writting AT based driver crates - ![crates.io](https://img.shields.io/crates/v/atat.svg)
 - [`embedded-nal`](https://github.com/rust-embedded-community/embedded-nal): An Embedded Network Abstraction Layer - ![crates.io](https://img.shields.io/crates/v/embedded-nal.svg)
 - [`embedded-storage`](https://github.com/rust-embedded-community/embedded-storage): An Embedded Storage Abstraction Layer
+- [`switch-hal`](https://github.com/rubberduck203/switch-hal): An "on"/"off" abstraction for input and output switches - ![crates.io](https://img.shields.io/crates/v/switch-hal.svg)
+
 
 ## Driver crates