select设置最大选中数

```js
  <FormItem className={[styles.proInput, styles.redDot].join(' ')}>
        {getFieldDecorator('leaders', {
          rules: formLeaderConfig.rules || [],
        })(
          <Select onSearch={searchList}>
            {formLeaderConfigOptions
              ? formLeaderConfigOptions.map(item => (
                <Select.Option label={item.name} disabled={getFieldValue('leaders') && getFieldValue('leaders').length === 10 && getFieldValue('leaders').findIndex(i=> i === item.id) === -1} value={item.id} key={item.id}>
                  {item.name}
                </Select.Option>
                ))
              : null}
          </Select>
        )}
      </FormItem>
```

关键 getFieldValue('leaders').findIndex(i=> i === item.id) === -1