update zh-cn/release-notes/api-change/v3.1-Release/readme.md.

Signed-off-by: Nzengyawen <zengyawen1@huawei.com>

zh-cn/release-notes/api-change/v3.1-Release/readme.md

@@ -4,7 +4,7 @@
 
 - [JS API差异报告](js-apidiff-v3.1-release.md)
 - [Native API差异报告](native-apidiff-v3.1-release.md)
+- [3.1 release相对于3.1 beta变更详细说明](changelog-v3.1-release.md)
 
 此外，本次还发布了OpenHarmony 3.2 Canary （API Version 9 Canary）版本：
 [JS API差异报告（API Version 9 Canary）](js-apidiff-v3.2-canary.md)
-