Support Horizontal split preview

[macintacos]

Is your feature request related to a problem? Please describe.

Right now, there's only a vertical split for the preview. Would be great to have a horizontal one, especially in situations where the width of your terminal is constrained.

[adilansari]

@dlvhdr would a change to input.SetWidth(xx) do the trick?

gh-dash/ui/components/prsidebar/prsidebar.go

Line 34 in 58a38ca

inputBox.SetHeight(common.InputBoxHeight)

[silky]

This would be so handy for those of us that wish to have this always-open on a portrait-style monitor ❤️ :)