message: mention 2-bit bmp support in CHANGES.md
diff: @@ -8,6 +8,10 @@ Rust image aims to be a pure-Rust implementation of various popular image format
  ## Changes
  +### Version 0.22 (unreleased)
  +
  +- Support loading 2-bit BMP images
  +
  ### Version 0.21
  - Updated README to use `GenericImageView`
  