Margin on Split pane divisor

[AdsonCicilioti]

Is your feature request related to a problem? Please describe. I'm not found on documentation an way for set margin to sideout of SplitPane divisors. In an aesthetic spaced customization, the shell chars content stay much near of splitpanel divisor. See:

Describe the solution you'd like Case not had, an option to set margin on side outs of SplitPanel Divisor will be a good feature for making aesthetic customization more spaced.

[AdsonCicilioti]

Or an shell_padding, that applies a space around shell content, it will do the work of windows_padding and an possible split_divisor_margin.

Actually, with window_padding and without splitpane_divisor_margin:

Proposal idea with shell_padding:

But with this proposal, we can see that the edge padding between panes will be a double space. So, only the splitpane_divisor_margin combined with window_padding will solve it.

We see: