Update CHANGELOG.md

Author: felix920506

CHANGELOG.md

@@ -22,6 +22,8 @@ These changes are available on the `master` branch, but have not yet been releas
   `tags`. ([#2520](https://github.com/Pycord-Development/pycord/pull/2520))
 - Added `Member.guild_banner` and `Member.display_banner` properties.
   ([#2556](https://github.com/Pycord-Development/pycord/pull/2556))
+- Added `played_seconds` function to `VoiceClient` to get elapsed time of the
+  playing audio file. ([#2587](https://github.com/Pycord-Development/pycord/pull/2587/))
 
 ### Fixed