features:
  - |
    Added support to cinder backup for use of the Zstandard compression
    algorithm.  To use it, set the ``backup_compression_algorithm`` to
    ``zstd`` in the cinder configuration file.  (The default value for
    this option is ``zlib``.)

Add release note for zstd compression
Add release note for zstd compression

This is the release note for Change
I32c98906847e3d10a846cf736ca848ea1608492e

Change-Id: I371894434450e36a8ee45b04473071ce3aa73a0b
