Update release notes

Author: klembot

docs/en/src/release-notes/2-9.md

@@ -1,5 +1,22 @@
 # 2.9 versions
 
+## 2.9.1
+
+Release Date: July 21, 2024
+
+## Bugs Fixed
+
+- Importing a story in browser Twine that replaces an existing one no longer creates duplicate stories.
+
+## Behind the Scenes
+
+- Many libraries used by Twine have been updated, and some which have been
+  superceded by built-in browser functionality have been removed.
+
+## Story Format Updates
+
+- SugarCube has been updated to version [2.37.0](http://www.motoslave.net/sugarcube/2/releases.php).
+
 ## 2.9.0
 
 Release Date: June 16, 2024
@@ -19,10 +36,9 @@ Release Date: June 16, 2024
 - The story library now sorts correctly by date.
 - An error in the Italian localization has been fixed.
 
-
 ## Story Format Updates
 
 - Chapbook has been updated to version
   [2.1.0](https://klembot.github.io/chapbook/guide/references/version-history.html#210-16-june-2024).
 - Harlowe has been updated to version
-  [3.3.9](https://twine2.neocities.org/#changes_3.3.8-changes-(jan-03,-2024)).
+  [3.3.9](<https://twine2.neocities.org/#changes_3.3.8-changes-(jan-03,-2024)>).