Incorrect type definition for clone()

[lloydk]

I think the type definition for the clone function should be changed from

export default function clone(color: Color): Color;

to

export default function clone(color: ColorObject): ColorObject;

The clone method doesn't copy the spaceId property so ColorObject isn't 100% technically correct but it's more correct than Color.

I would have created a PR but I couldn't figure out how to get the type tests to run.

[lloydk]

This was fixed in #291.