adding upscale result in the generation

[anelfandagoblin]

first of all, thanks for this great tool

sometimes i have to down scale an upscaled image to edit stuff then upscale again, but i just want the old upscale result for consistency. storing upscaled results in the generation history can be very useful for this fixing process

[tzvikanoy]

sidestepping the issue (i'm not a part of the dev team), it's common practice in image editing to always work on a duplicate layer, so that no matter what - there'll be an untouched milestone to fall back to.