Function lerp

lerp(xs, ys): Mapper<number>
Returns a linear interpolation function for given pivot points.

Notes: Don't mutate xs and ys arrays after creating this function since data from these arrays is read during interpolation.
Parameters
- xs: ArrayLike<number>
  The array of X coordinates of pivot points in ascending order.
- ys: ArrayLike<number>
  The array of corresponding Y coordinates of pivot points.
Returns Mapper<number>
The function that takes X coordinate and returns an interpolated Y coordinate.
Example
```
const f = lerp(xs, ys);
const y = f(x);
```