bugfix: wrong selected value in different fontSize/itemHeight

[aliunco]

If you are using certain functionalities to enable responsive design, such as scaled font sizes, height adjustments, and boundaries, you may encounter bugs where incorrect values are passed through the onChange function.

In this branch, I have optimized the calculation of this value and eliminated the bug. 🙃

Thanks for reviewing this PR (in advance)

[tranminhkhang7]

Pls refer to this issue. That solves my problem:

https://github.com/erksch/react-native-wheely/issues/49