adding changelog entry

Author: devnexen

CHANGELOG.md

@@ -21,6 +21,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - Added `SOF_TIMESTAMPING_OPT_ID` and `SOF_TIMESTAMPING_OPT_TSONLY` to `nix::sys::socket::TimestampingFlag`.
   ([#2048](https://github.com/nix-rust/nix/pull/2048))
 - Enabled socket timestamping options on Android. ([#2077](https://github.com/nix-rust/nix/pull/2077))
+- Added `SO_SETFIB` and `SO_USER_COOKIE` to `nix::sys::socket::sockopt` for FreeBSD.
+  ([#2085](https://github.com/nix-rust/nix/pull/2085))
 
 ### Changed