多选框支持已选项的自定义渲染

[EmiyaYang]

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

What problem does this feature solve?

开发者可以自定义 select 框内已选项的具体渲染方式, 可以扩展已选项拖拽排序等功能

What does the proposed API look like?

selectionRender: (selections) {
    return this.$createElement(...);
}

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[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.