[Feature]: Slider thumb: Dont add extra px to position

[MickL]

Describe the feature

Ive noticed that to the position of the thumb an extra px amount is added:

This results in the thumb to never be centered at the position where he should be:

The white line shows the "should".

I guess this prop is used so the start and the end is aligned with the track, but it would be great if this can be disabled so we just have the correct percentage.

Additional information

• I intend to submit a PR for this feature.
• I have already implemented and/or tested this feature.