Feature request: Configuration option for changing default pane stacking

[i8x3]

Hello!

Currently, there is no way to change the default the way panes stack in the configuration. In src/screen/dashboard.rs, I saw that there was already a comment that said "Default split could be a config option" (line 1239).

// Default split could be a config option.
let axis = pane_grid::Axis::Horizontal;

I modified the line right under it, changing Horizontal to Vertical, built it, and it worked just like I hoped for. If you guys could make this an option in the configuration, that would be great.

Thank you very much!