Add a test status section to display testgrid status.

Signed-off-by: Siyuan Zhang <[email protected]>

README.md

@@ -133,6 +133,19 @@ Now it's time to dig into the full etcd API and other guides.
 [security]: https://etcd.io/docs/latest/op-guide/security
 [tuning]: https://etcd.io/docs/latest/tuning
 
+## Test Status
+
+etcd uses Kubernetes' prow infrastructure to run CI jobs. The test results can be viewed at [testgrid](https://testgrid.k8s.io/sig-etcd).
+
+| Tests  | Status  |
+| -----  | ------  |
+| periodics e2e-amd64  | [![sig-etcd-periodics/ci-etcd-e2e-amd64](https://testgrid.k8s.io/q/summary/sig-etcd-periodics/ci-etcd-e2e-amd64/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-periodics/ci-etcd-e2e-amd64)  |
+| presubmit build      | [![sig-etcd-presubmits/pull-etcd-build](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-build/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-build)  |
+| presubmit e2e-amd64  | [![sig-etcd-presubmits/pull-etcd-e2e-amd64](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-e2e-amd64/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-e2e-amd64)  |
+| presubmit unit-test  | [![sig-etcd-presubmits/pull-etcd-unit-test](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-unit-test/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-unit-test)  |
+| presubmit verify     | [![sig-etcd-presubmits/pull-etcd-verify](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-verify/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-presubmits/pull-etcd-verify)  |
+| postsubmit build     | [![sig-etcd-postsubmits/post-etcd-build](https://testgrid.k8s.io/q/summary/sig-etcd-postsubmits/post-etcd-build/tests_status?style=svg)](https://testgrid.k8s.io/q/summary/sig-etcd-postsubmits/post-etcd-build)  |
+
 ## Contact
 
 * Email: [etcd-dev](https://groups.google.com/g/etcd-dev)