add student assistant

dashboard/src/locales/zh-Hans/auth/index.ts

@@ -4,6 +4,8 @@ const items = {
   "auth.role.manager": "管理员",
   "auth.role.editor": "编辑者",
   "auth.role.member": "成员",
+  "auth.role.student": "学生",
+  "auth.role.assistant": "助理老师",
   "auth.role.unknown": "未知",
   "auth.type.user": "用户",
   "auth.type.group": "群组",