CHANGELOG.md: Add dom0/domU zstd compression support

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Ian Jackson <ian.jackson@citrix.com>

CHANGELOG.md

@@ -13,6 +13,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
  - Switched MSR accesses to deny by default policy.
  - Intel Processor Trace support (Tech Preview)
  - Named PCI devices for xl/libxl
+ - Support for zstd-compressed dom0 (x86) and domU kernels
 
 ### Removed / support downgraded