chore: add changelog entry

Author: Soheab

CHANGELOG.md

@@ -17,6 +17,9 @@ These changes are available on the `master` branch, but have not yet been releas
   ([#2711](https://github.com/Pycord-Development/pycord/pull/2711))
 - Added `RawMessageUpdateEvent.new_message` - message update events now contain full
   message objects ([#2780](https://github.com/Pycord-Development/pycord/pull/2780))
+- Added support for setting guild-specfic `avatar`, `banner`, and `bio` for the bot user
+  through `Member.edit`.
+  ([#2908](https://github.com/Pycord-Development/pycord/pull/2908))
 
 ### Changed