Add option to maintain aspect ratio on resize

[BritishWerewolf]

In some cases it is required to resize an image, but maintain the aspect ratio.
This is usually because we want to pad the image.

Here's an example of something I was thinking of.

const image = await RawImage.fromURL("https://picsum.photos/600/400");
const resized = await image.resize(300, null); // 300x200
const padHeight = (300 - image.height) / 2;
const padded = await image.pad([0, 0, padHeight, padHeight]); // 300x300

In this example, we resize the image, maintain the aspect ratio and then pad either side.