Update changelogs from fern repo (#838)

Co-authored-by: jsklan <[email protected]>

Author: fern-support

fern/products/sdks/overview/typescript/changelog/2025-09-16.mdx

@@ -1,3 +1,7 @@
+## 2.12.0
+**`(feat):`** Add support for custom sections in the README.md via `customSections` config option.
+
+
 ## 2.11.2
 **`(fix):`** Websocket client generation compiles when there are no query parameters and when the auth 
 scheme has custom authentication headers.