[Feature] Choose memory cards / save states folder

[czrcbl]

Hi, Thanks for the this project, it works really well.

I sync my game saves among my devices using Syncthing, it works with most emulators on android, since they keep the saves in a "public" folder. AetherSX2 keeps the saves under the android/data folder, which cannot be accessed by most apps including Syncthing. Would it be possible to have an option to choose the memory cards folder, like the PCSX2 has on the desktop?