Update changelog

Author: facelessuser

docs/changelog.md

@@ -17,6 +17,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * Backslash Unescape IDs set via `attr_list` on `toc` (#1493).
+* `md_in_html` should now process content inside "markdown" blocks a similar way
+  as they are parsed outside of "markdown" blocks giving a more consistent
+  expectation to external extensions (#1503).
 
 ## [3.7] -- 2024-08-16