Prepare to release 2.3.9

Author: colinodell

CHANGELOG.md

@@ -6,6 +6,8 @@ Updates should follow the [Keep a CHANGELOG](https://keepachangelog.com/) princi
 
 ## [Unreleased][unreleased]
 
+## [2.3.9] - 2023-02-15
+
 ### Fixed
 
 - Fixed autolink extension not detecting some URIs with underscores (#956)
@@ -516,7 +518,8 @@ No changes were introduced since the previous release.
     - Alternative 1: Use `CommonMarkConverter` or `GithubFlavoredMarkdownConverter` if you don't need to customize the environment
     - Alternative 2: Instantiate a new `Environment` and add the necessary extensions yourself
 
-[unreleased]: https://github.com/thephpleague/commonmark/compare/2.3.8...main
+[unreleased]: https://github.com/thephpleague/commonmark/compare/2.3.9...main
+[2.3.9]: https://github.com/thephpleague/commonmark/compare/2.3.8...2.3.9
 [2.3.8]: https://github.com/thephpleague/commonmark/compare/2.3.7...2.3.8
 [2.3.7]: https://github.com/thephpleague/commonmark/compare/2.3.6...2.3.7
 [2.3.6]: https://github.com/thephpleague/commonmark/compare/2.3.5...2.3.6