Automatically add label `workflowin::in qa` when assign issue to QA

Refer: gitlab-cn/gitlab#1071 (comment 581444)

Can we automate this somehow with triage ops? Like when an issue is assigned to a QA, automatically add workflowin qa.

Changes

Improve #2 (closed), add workflowin qa together in the processor.

Note that if the processor name is not appropriate, it needs to be refactored.

/cc @qianzhangxa