doc: add changelog

Author: cdalvaro

changelog/68784.fixed.md

@@ -0,0 +1,11 @@
+Fix `pip.installed` state reinstalling packages on every run even when the
+correct version is already present:
+
+- `pip.list_freeze_parse` now normalizes package names (lowercase, hyphens)
+  consistent with `pip.list`, so that packages whose `pip freeze` name uses
+  underscores or mixed case (e.g. `requests_oauthlib`) are correctly detected
+  as already installed when looked up by their normalized name.
+- The post-install check in `pip.installed` now also recognizes
+  `"Requirement already satisfied:"` (modern pip ≥ 10.0) in addition to the
+  old `"Requirement already up-to-date:"` message, preventing packages
+  confirmed as already present from being falsely reported as changed.