Document changes and document the alloc feature

Author: adri326

embedded-hal-bus/CHANGELOG.md

@@ -7,7 +7,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
-(Add unreleased changes here)
+- Added the `alloc` feature.
+- Added a new `RcDevice` for I2C and SPI, a reference-counting equivalent to `RefCellDevice`.
 
 ## [v0.2.0] - 2024-04-23
 

embedded-hal-bus/README.md

@@ -34,6 +34,7 @@ provides mechanisms to obtain multiple `I2c` instances out of a single `I2c` ins
   `std::error::Error` for `DeviceError`.
 - **`async`**: enable `embedded-hal-async` support.
 - **`defmt-03`**: Derive `defmt::Format` from `defmt` 0.3 for enums and structs.
+- **`alloc`**: enable implementations using `alloc` (for instance, `spi::RcDevice`, which makes use of `alloc::rc::Rc`)
 
 ## Minimum Supported Rust Version (MSRV)