Multi-thumb option

## Describe the Feature
Right now we only have one "grip" option. It would be nice to have multiple grips. Two would be a good start.

## Possible Implementations
For Android probably this one - https://github.com/apptik/MultiSlider

For iOS probably this one - https://github.com/yonat/MultiSlider

## Related Issues

未指定任何文件、测试或入口点。先审查当前的 React Native slider API 及其 iOS Slider 和 Android SeekBar 集成，然后评估关联的 MultiSlider 选项；当在两个平台上通过一个达成一致的 API 一致地支持两个滑柄时，即视为完成。

由索引模型根据 Issue 内容生成。