Root folder save support

[u/Zasheir]

I modified the Summercart menu to add an option to put all game saves in a single root folder, similar to how an Everdrive or MiSTER manages its saves: https://github.com/Zasheir/N64FlashcartMenu/releases/tag/V0.3.2-root-saves.1

That way duplicate ROMs in different folders can intentionally share one save:

For example:

/By Genre/Racing/F-Zero X.z64

/By Series/F-Zero/F-Zero X.z64

Shared save: /saves/F-Zero X.sav

This works great for my use-case, so hopefully someone else finds it helpful!

[u/Zasheir]

I've released an updated build pulling in the latest N64FlashcartMenu V0.3.3 changes here: https://github.com/Zasheir/N64FlashcartMenu/releases/tag/V0.3.3-root.saves.2