Draft: Initial support for I2S with a working example.

Co-authored-by: @brainstorm <brainstorm@nopcode.org>

embassy-nrf/src/chips/nrf52840.rs

@@ -164,6 +164,9 @@ embassy_hal_common::peripherals! {
 
     // PDM
     PDM,
+
+    // I2S
+    I2S,
 }
 
 #[cfg(feature = "nightly")]
@@ -285,6 +288,8 @@ impl_saadc_input!(P0_29, ANALOG_INPUT5);
 impl_saadc_input!(P0_30, ANALOG_INPUT6);
 impl_saadc_input!(P0_31, ANALOG_INPUT7);
 
+impl_i2s!(I2S, I2S, I2S);
+
 pub mod irqs {
     use embassy_cortex_m::interrupt::_export::declare;