Ability to save Reading Panel layout dimensions

I’d like the ability to save my two-panel layout dimensions. Unlike the previous request, I prefer a less dense email list panel, so I have to drag my reading panel over to the left every time I open Mailspring.

Maybe auto-saving the dimensions of the layout every time it’s adjusted would handle this?

And also, thanks to everyone involved for the most gorgeous and best email client out there. I’ve got it installed on every system I have.

(Originally posted by mscott5861 on GitHub.)