Ability to flip screen vertically

[William-Kirk]

Currently when playing, you have to use the 4 arrow buttons with your right hand while playing, but most people are used to using their left hand for arrow keys. This makes it somewhat uncomfortable and difficult to play.

A solution that I think would work well is simply the ability to flip the screen upside down and play holding the calculator upside down. It's a comfortable position and it allows the left hand to use the arrow keys.

I've considered using 4 keys on the left as joystick and the arrows as buttons instead, but the travel distance between buttons was just too much.

I cloned the repo and started working on this myself, but if it's something that could be added simply into the main branch, I think that'd be pretty great.