allow change of parameters for easing functions

For most of the easing functions listed, some magic values are hardcoded into the formula, it would be cool to be able to configure them.
e.G: ``easeOutExpo``

``function easeOutExpo(x: number): number {
return x === 1 ? 1 : 1 - Math.pow(2, -10 * x);

}``
why especially the power of 2? why -10 * x as the exponent and not -7 or something? would be cool to be able to try around with those values a bit ;)