Stay on line number when changing compared files, modes and layouts

[Profpatsch]

I often want to see the same conflict in another view, but it always changes the line when I change layout, mode, or compared files.

[errael]

@Profpatsch I have a question about this issue. With the latest version of https://github.com/errael/splice9, a pure vim9script port of splice (no python, additional features, can use same config) it keeps the cursor position (only for mode changes so far, I think I'll extend it). But I'm thinking centering the cursor line, like z. would be better. Comment?