removeBuilder optional

[federicodesia]

Hi! First of all, thank you for this package!

Would it be possible to make the removeBuilder parameter optional?
In this way it would avoid repeating the code of the itemBuilder parameter if the animations are the same.

[zaikavova]

Hi! I guess it has a different meaning of use, sometimes you have the same animation just reversed, so you have options to make a separate method and just transform the animation value to be reversed.