Support linearGradient/radialGradient when using fillStyle

Currently, we can only pass solid colors, but it would be great to have the ability to apply gradient colors directly to paths when transforming them on the canvas.

const gradient = ctx.createLinearGradient(x1, y1, x2, y2);
gradient.addColorStop(0, 'red');
gradient.addColorStop(1, 'blue');

ctx.fillStyle = gradient;

At present, https://github.com/catdad/canvas-confetti/issues/80#issuecomment-2511208926 works for me.