Gradient transition of color(s) between two position.
import { LinearGradient, Square } from "pencil.js";
const position = [100, 200];
const size = 200;
const startPosition = [0, 0];
const endPosition = [size, size];
const square = new Square(position, size, {
fill: new LinearGradient(startPosition, endPosition, {
0: "red",
0.5: "yellow",
1: "green",
}),
});