update changelog

Author: aslilac

CHANGELOG.md

@@ -12,6 +12,7 @@
 - Multiple open instances of the extension could potentially clobber writes to
   `~/.ssh/config`. Updates to this file are now atomic.
 - Add support for `anysphere.remote-ssh` Remote SSH extension.
+- Use `--header-command` properly when starting a workspace.
 
 ## [v1.9.0](https://github.com/coder/vscode-coder/releases/tag/v1.9.0) 2025-05-15