Custom Interpolator [proposal]

[julienvincent]

It might be a good api addition to allow for custom interpolators. It could look something like this:

const anim = new Animated.Value(0)

...

const interpolatedValue = anim.interpolate((value) => {
  // return custom interpolation based on value
})

An example use case would be using D3's powerful interpolators (like their SVG path interpolator) along with Animatedjs

[julienvincent]

I have submitted a PR for this functionality. See #68