Swap screen that displays single-screen games on dual-screen consoles

Most of the time when I’d play something like a GameBoy or GameBoy Advance game on my DS Lite or 3DS the game would always be on the top, though iirc the DS Lite would let you switch between top and bottom. An option to swap which screen non-Desmume/Citra emulators display on would be nice on the Partycon 2S and S3D :]

I can work on this.