update docs

Signed-off-by: NAnnie_wang <annie.wangli@huawei.com>

en/application-dev/reference/apis/Readme-EN.md

@@ -233,6 +233,7 @@
   - [@ohos.data.ValuesBucket (Value Bucket)](js-apis-data-valuesBucket.md)
 
 - File Management
+  - [@ohos.file.backup (Backup and Restoration)](js-apis-file-backup.md)
   - [@ohos.file.cloudSyncManager (Device-Cloud Synchronization Management)](js-apis-file-cloudsyncmanager.md)
   - [@ohos.file.environment (Directory Environment Capability)](js-apis-file-environment.md)
   - [@ohos.file.fileAccess (User File Access and Management)](js-apis-fileAccess.md)