refactor: Moved all layouts into their own files

[Nick-Munnich]

As discussed on Discord. Also adjusted the docs for consistency.

I am not entirely sold on the matrix transform assignments happening in the separate file as well, thoughts?

[caksoylar]

Maybe I missed the aforementioned conversation -- I don't think pulling out layouts that simply import and modify the common layouts are necessary, is it? It adds a lot of noise for a few lines of config.

[Nick-Munnich]

Maybe I missed the aforementioned conversation -- I don't think pulling out layouts that simply import and modify the common layouts are necessary, is it? It adds a lot of noise for a few lines of config.

Yeah, that's the part I wasn't certain on myself. I think it would make sense to leave that kind of thing in, but then that raises the question of how to handle situations like the Kyria correctly. I like the way you defined it originally, but I'm not sure how best to extend that to a convention.

[caksoylar]

My thinking would be that if a keys property is to be defined then you should pull it off to a separate file. You'd do that even if the keyboard only has one physical layout, which we seem to have left in the dtsi/overlay before this PR.