Adapt Print-in-Place laptop stand to hold iPad in Portrait

This adds two horizontal members that drop in to the Print-in-Place laptop stand to allow it to hold an iPad, iPad Mini, or iPhone in portrait mode.

This is an add-on to https://www.prusaprinters.org/prints/40829-print-in-place-folding-laptop-stand/

You'll need to make that first, then print these two horizontal members