handleStyle prop does not overwrite styles

If a property exists on the handle, you basically can't overwrite it with a new value.
Example:

<Slider handleStyle={{transform: 'scale(2.0)'}}/>

because there already exists a transform property on the handle

transform: translateX(-50%);

while

<Slider handleStyle={{backgroundColor: 'red'}}/>

works

    background-color: red;
    left: 50%;
    right: auto;
    transform: translateX(-50%);

I haven't delved into the codebase but I'm guessing the handleStyle prop is not overriding the default styles properly.
This seems like a pretty easy fix. I don't mind submitting a PR.

Start by tracing how the Slider's handleStyle prop is applied alongside the handle's default styles. Reproduce the scale(2.0) example and compare it with the working backgroundColor case; done means a handleStyle transform replaces the default translateX(-50%) while existing style overrides continue to work.