Newsletter 23: Add embedded-hal-mock release

Author: dbrgn

content/2020-01-30-newsletter-23.md

@@ -33,6 +33,8 @@ If you want to mention something in [the next newsletter], send us a pull reques
 
 <!-- TODO Add news related to embedded Rust that are not about new crates releases here -->
 
+- [embedded-hal-mock](https://github.com/dbrgn/embedded-hal-mock/) has released 0.7.1 on crates.io with [support for error expectations](https://docs.rs/embedded-hal-mock/0.7.1/embedded_hal_mock/i2c/index.html#testing-error-handling). This means that you can now unit test the error handling logic of your embedded-hal driver crates.
+
 - TODO(remove, this is an example) "const generics" has landed in nightly!
 
 - TODO(remove, this is an example) the Rust compiler has gained cross compilation support for the Xtensa architecture!