[Feature Request] Pressing Select to flip top and bottom screens

[HeteroChromia420]

For the sake of accessibility (as well has having a place to track this feature request), i decided to open up this github issue.

as the title does imply, this feature would flip the top and bottom screens with a press of a button, select being my choice. This feature would allow DSes that have a broken top display or have undergone the "Game Boy Macro" Mod to still use this homebrew app.