Function scale

scale(
    colours: Colourish[],
    numberOfSteps: number,
    opts?: Partial<ColourInterpolationOpts>,
): string[]
Produces a stepped scale of colours.
```
const steps = Colour.scale([ `red`, `green` ], 10);
for (const step of steps) {
 // A CSS colour string
}
```
cssLinearGradient can produce a smooth gradient in CSS on the basis of the stepped colours.
Parameters
- colours: Colourish[]
- numberOfSteps: number
- opts: Partial<ColourInterpolationOpts> = {}
Returns string[]