Merge pull request #8163 from mengjiao-liu/add-email

Add mengjiao-liu' email to sigs.yaml

Author: k8s-ci-robot

sigs.yaml

@@ -3630,6 +3630,7 @@ workinggroups:
     - github: mengjiao-liu
       name: Mengjiao Liu
       company: DaoCloud
+      email: [email protected]
     - github: pohly
       name: Patrick Ohly
       company: Intel