[doc] update the release Readme.md
# Release Notes
Release Notes - Apache ServiceComb - Version service-center-2.1.0
-### Bug
+## Bug
- [SCB-2400](https://issues.apache.org/jira/browse/SCB-2400) - Govern api return empty schemaIds
- [SCB-2403](https://issues.apache.org/jira/browse/SCB-2403) - Start up failed when upgrade sc version
- [SCB-2404](https://issues.apache.org/jira/browse/SCB-2404) - Return internal properties when list all microservices
- [SCB-2411](https://issues.apache.org/jira/browse/SCB-2411) - Try dlock before start retirement job
- [SCB-2418](https://issues.apache.org/jira/browse/SCB-2418) - Fix etcd metrics not correct
- [SCB-2420](https://issues.apache.org/jira/browse/SCB-2420) - Can not delete unused role
-### New Feature
+## New Feature
- [SCB-2402](https://issues.apache.org/jira/browse/SCB-2402) - Support synchronization of multiple registries
- [SCB-2401](https://issues.apache.org/jira/browse/SCB-2401) - Append inner properties when heartbeat success
- [SCB-2408](https://issues.apache.org/jira/browse/SCB-2408) - Add put instance service
- [SCB-2414](https://issues.apache.org/jira/browse/SCB-2414) - Add schema retire cron job
- [SCB-2415](https://issues.apache.org/jira/browse/SCB-2415) - Add schema ref
- [SCB-2419](https://issues.apache.org/jira/browse/SCB-2419) - Add govern service
-### Improvement
+## Improvement
- [SCB-2405](https://issues.apache.org/jira/browse/SCB-2405) - Use dlock instead
- [SCB-2406](https://issues.apache.org/jira/browse/SCB-2406) - Using cari's mongo db client
- [SCB-2407](https://issues.apache.org/jira/browse/SCB-2407) - Using cari db client
