Image upscaling

[YelovSK]

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Feature details

On-demand upscaling of images using e.g. waifu2x. A feature like this exists in aw-man, although I did not try it. The use case for me is viewing manga at a larger size on a high-res horizontal display without losing too much quality.

Probably too niche to implement, but I figured I'd throw this out here.

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