docs: update changelog for PR #784

Author: ClementTsang

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#760](https://github.com/ClementTsang/bottom/pull/760): Add a check for whether bottom is being run in a terminal.
 - [#766](https://github.com/ClementTsang/bottom/pull/766): Add FreeBSD support.
 - [#774](https://github.com/ClementTsang/bottom/pull/774): Add half page scrolling with `ctrl-u` and `ctrl-d`.
+- [#784](https://github.com/ClementTsang/bottom/pull/784): Add ZFS ARC support.
 
 ## [0.6.8] - 2022-02-01