Improve the QWERTY correction layout

[Seterplus]

I assume this is mainly for mobile systems. Currently this supports errors where the keys are adjacent in the same row, but I found I often wrongly type "i" as "j" too.

I think the point is that, when I type with two hands, my fingers are tend to keep close to "d" and "j", so when I type a wrong key it's likely because my finger moves not far enough to reach the correct one - that said, the wrong key should be the one a bit closer to "d" or "j". I won't mistype "j" as "i" but only "i" as "j". Similarly, I won't mistype "d" as "s" but only "s" as "d".

So my suggestion for the QWERTY correction layout would be that for each key we only consider (or prioritize) the adjacent one or two keys towards "d" or "j".

Maybe there are some researchs for better solutions but I don't think I'm such an expert XD