add containerservice (#21713)

Author: xiaoxuqi-ms

.github/pull_request_assignment.yml

@@ -87,7 +87,7 @@
 
 
 - rule:
-    paths: "specification/@(providerhub|sql|appplatform|deviceupdate|servicelinker|imagebuilder|throttling|secretmanagementtestsvc)/**"
+    paths: "specification/@(providerhub|sql|appplatform|deviceupdate|servicelinker|imagebuilder|throttling|secretmanagementtestsvc|containerservice)/**"
     reviewers:
       - raych1
       - xiaoxuqi-ms