Add mention of HID class crate

Author: Tom

README.md

@@ -29,7 +29,8 @@ Hardware driver crates
 Class crates
 ------------
 
-* [usbd-serial](https://github.com/mvirkkunen/usbd-serial) - CDC-ACM serial port class
+* [usbd-serial](https://github.com/mvirkkunen/usbd-serial) [![Crates.io](https://img.shields.io/crates/v/usbd-serial.svg)](https://crates.io/crates/usbd-serial) - CDC-ACM serial port class
+* [usbd-hid](https://github.com/twitchyliquid64/usbd-hid) [![Crates.io](https://img.shields.io/crates/v/usbd-hid.svg)](https://crates.io/crates/usbd-hid) - HID class
 
 TODO
 ----