Function interpolate

Calculates a point in-between a line's start and end points.

Param: amount

Interpolation amount

Param: aOrLine

Line, or first point

Param: pointBOrAllowOverflow

Second point (if needed) or allowOverflow.

Param: allowOverflow

If true, interpolation amount is permitted to exceed 0..1, extending the line.

Returns

interpolate(amount, a, pointB, allowOverflow?): Point
Calculates a point in-between a and b.

If an interpolation amount below 0 or above 1 is given, and allowOverflow_ is true, a point will be returned that is extended past line`. This is useful for easing functions which might briefly go past the limits.
```
import { Lines } from 'https://unpkg.com/ixfx/dist/geometry.js'

// Get {x,y} at 50% along line
Lines.interpolate(0.5, line);

// Get {x,y} at 80% between point A and B
Lines.interpolate(0.8, ptA, ptB);
```
Parameters
- amount: number
  Relative position, 0 being at a, 0.5 being halfway, 1 being at b
- a: Point
  Start
- pointB: Point
  End
- OptionalallowOverflow: boolean
Returns Point
Point between a and b
interpolate(amount, line, allowOverflow?): Point
Calculates a point in-between line's start and end points.
```
import { Lines } from 'https://unpkg.com/ixfx/dist/geometry.js'

// Get {x, y } at 50% along line
Lines.interpolate(0.5, line);
```
Any additional properties from b are returned on the result as well.
Parameters
- amount: number
  0..1
- line: Line
  Line
- OptionalallowOverflow: boolean
  If true, interpolation amount is permitted to exceed 0..1, extending the line
Returns Point