Add possibility to set default type of diff for images (Two-up, blend, split, pixeldiff)
When reviewing PR that contains alot of images I usually want to see either pixeldiff or split so i can easily see the differences in the images. Two-up is propably the worst image diff to see exactly what changed.

I would appreciate either some settings in profile or the selection being "permanent" for atleast one pullrequest (or rather one webpage reload) - if i select pixeldiff once, it will remember this choice.

Thanks