Update changelog

Author: Taaku18

CHANGELOG.md

@@ -11,6 +11,7 @@ however, insignificant breaking changes do not guarantee a major version bump, s
 ### Fixed
 - `?alias make/create` as aliases to `?alias add`. This improves continuity between the bot and its command structure. ([PR #3195](https://github.com/kyb3r/modmail/pull/3195))
 - Loading the blocked list with the `?blocked` command takes a long time when the list is large. ([PR #3242](https://github.com/kyb3r/modmail/pull/3242))
+- Reply not being forwarded from DM. (PR [#3239](https://github.com/modmail-dev/modmail/pull/3239))
 
 # v4.0.2