Add 'avr_delay' as a dependency and expose crate

Cargo.toml

@@ -29,6 +29,7 @@ all-mcus = []
 
 [dependencies]
 avr-config = "1.0"
+avr_delay = "0.3"
 avr-std-stub = { version = "1.0", optional = true }
 const_env--value = "0.1"
 target-cpu-macro = "0.1"

src/lib.rs

@@ -26,6 +26,9 @@ pub mod modules;
 /// Configuration for the currently-targeted microcontroller.
 pub use avr_config as config;
 
+/// Delay routines.
+pub use avr_delay as delay;
+
 mod register;
 mod pin;