Function invert

Inverts one or more axis of a point

invert({x:10, y:10}); // Yields: {x:-10, y:-10}
invert({x:10, y:10}, `x`); // Yields: {x:-10, y:10}

invert(pt, what?): Point
Parameters
- pt: Point | Point3d
  Point to invert
- what:
      | "x"
      | "y"
      | "z"
      | "both" = ...
  Which axis. If unspecified, both axies are inverted
Returns Point