function makeImagesEqualSize(expected, actual) {
  const height = Math.max(expected.height, actual.height);
  const width = Math.max(expected.width, actual.width);
  actual.image = createCompareCanvas(width, height, actual.image);
  expected.image = createCompareCanvas(width, height, expected.image);
}
Create a canvas that can fit both `expected` and `actual` image.
Makes it easier to compare images (and also nicer diff result).
@param {*} expected
@param {*} actual