级联下拉选择组件增加多选支持

[jiangxiaoyuboy]

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

解决下拉多选的功能，不用树形控件的原因是，其样式不符合项目需求，而级联的样式符合，所以建议加上级联下拉多选功能，谢谢

What does the proposed API look like?

建议加上级联下拉多选功能

[github-actions]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days

[MinMinEr]

同求

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.