feat: take into account threshold for gradient calc

[voidpls]

When threshold is >1, gradient calculation doesn't take threshold into account. The "minimum" color of a gradient is often not the defined start of the gradient, depending on starboard config.

Fix works well in preliminary testing, but haven't extensively tested.

Also switches from Math.floor to bitwise flooring (~~), due to Math.floor not working properly with negatives

[SimonLeclere]

< hahaha

[SimonLeclere]

Why using +1 -1 ?

[voidpls]

After order of operations, it's:
Math.max(Math.min(~~((stars - threshold +1) - ((1 / color.max )* color.colors.length)), color.colors.length - 1), 0);
Which is based off the original code. From testing, the logic appears to work correctly, but you should test yourself as well

[SimonLeclere]

My bad

[SimonLeclere]

I'm currently updating (and repairing the module), i'll merge your pr after that :)
Sorry for the delay lol