add changelog entry

Author: Emilgardis

CHANGELOG.md

@@ -5,6 +5,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- #684 - Enable cargo workspaces to work from any path in the workspace, and make path dependencies mount seamlessly.
 - #494 - Parse Cargo's --manifest-path option to determine mounted docker root
 - #718 - remove deb subcommand.
 - #714 - use host target directory when falling back to host cargo.