message: Update changelog with async decryption APIs
diff: @@ -10,6 +10,11 @@ to 1.0.0 are beta releases.
  ## [Unreleased]
  ### Added
  +- Asynchronous APIs for decryption:
  + - `age::Decryptor::new_async()`
  + - `age::decryptor::RecipientsDecryptor::decrypt_async()`
  + - `age::decryptor::RecipientsDecryptor::decrypt_async_with_callbacks()`
  + - `age::decryptor::PassphraseDecryptor::decrypt_async()`
  - `age::armor::ArmoredReader`, which can be wrapped around an input to handle
  a potentially-armored age file.
  - `age::armor::ArmoredWriter`, which can be wrapped around an output to
  