a-select 没有自定义 label

[xwxn20180918]

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

What problem does this feature solve?

希望可以有自定义label

What does the proposed API look like?

[xwxn20180918]

<Select
prefix="User"
defaultValue={['lucy']}
mode="multiple"
style={{ width: 200 }}
onChange={handleChange}
options={[
{ value: 'jack', label: 'Jack' },
{ value: 'lucy', label: 'Lucy' },
{ value: 'Yiminghe', label: 'yiminghe' },
{ value: 'disabled', label: 'Disabled', disabled: true },
]}
/>

比如和react 类型 使用 prefix="User"，就可以自定义前缀label