docs(changelog): version v0.28.1 [citest skip]

Update changelog and .README.html for version v0.28.1

Signed-off-by: Matt Willsher <matt@monki.org.uk>

Author: mattwillsher

CHANGELOG.md

@@ -1,6 +1,13 @@
 Changelog
 =========
 
+[v0.28.1] - 2025-11-08
+--------------------
+
+### Bug Fixes
+
+- fix: Allow specifying OS vars from playbook_dir (#330)
+
 [v0.28.0] - 2025-09-07
 --------------------