feat: horizontal/vertical padding

[ilyazz-zzayli]

This PR allows the user to specify different padding-values for the left and right sides (horizontal) and for the top and bottom sides (vertical).

[stevearc]

Thanks for the PR, but I do not want to merge this. There's a fine balance between adding customization options and making the config options too complex. In this case, you can already achieve this behavior in your own config by using the float.override function and changing the row/col/width/height of the window. Because it's already possible (albeit with slightly more effort), I don't think it's worth adding more special cases to the config shape.