Add workflow:done label when issue is closed

What does this MR do

We use a series of workflow:: labels on the https://jihulab.com/gitlab-cn/gitlab to mark the status of an issue:

• workflow::in dev
• workflow::in review
• workflow::in qa
• workflow::in done
• workflow::in blocked

And, we use Issue Boards (Kanban) to browse and manage issues in a milestone, just like: https://jihulab.com/groups/gitlab-cn/-/boards/4607?milestone_title=15.1

When we finish an issue, we can drag the issue tab from workflow:in dev list to Closed list, but the label in it has not changed, we expect that its label will automatically change to workflow:done .