Add changelog entry for css_modules_export_mode configuration

Author: justin808

CHANGELOG.md

@@ -17,6 +17,7 @@ Changes since the last non-beta release.
 
 ### Added
 
+- **Support for `css_modules_export_mode` configuration option**. [PR #TBD](https://github.com/shakacode/shakapacker/pull/TBD) by [justin808](https://github.com/justin808). Adds `css_modules_export_mode` setting in `shakapacker.yml` to control CSS Modules export style. Set to `"named"` (default, v9+ behavior with true named exports) or `"default"` (v8 behavior with default export object). Allows teams to opt into v8-style exports for easier migration from v8 or when using TypeScript with strict type checking.
 - **Support for `javascript_transpiler: 'none'`** for completely custom webpack configurations. [PR #799](https://github.com/shakacode/shakapacker/pull/799) by [justin808](https://github.com/justin808). Allows users with custom webpack configs to skip Shakapacker's transpiler setup and validation by setting `javascript_transpiler: 'none'` in `shakapacker.yml`. Useful when managing transpilation entirely outside of Shakapacker's defaults.
 
 ## [v9.3.0] - November 2, 2025