Add changelog.

Author: Dirbaio

CHANGELOG.md

@@ -10,6 +10,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 - `Error` traits for Can, SPI, I2C and Serial are implemented for Infallible
 
+### Changed
+- `spi/blocking`: unified traits into `Read`, `Write`, `ReadWrite`.
+- `spi/blocking`: traits now enforce all impls on the same struct (eg `Read` and `Write`) have the same `Error` type.
+- `spi/blocking`: renamed Transactional `exec` to `batch`.
+- `spi/blocking`: Added `read_batch`, `write_batch` methods.
+
 ## [v1.0.0-alpha.6] - 2021-11-19
 
 *** This is (also) an alpha release with breaking changes (sorry) ***