[Boxart] Add Filename for Boxarts

[TharathielCB]

Description

Adding a 3rd option to show boxarts in the menu. If the boxart is named as the file you can store romspecific boxarts. This might be helpful for e.g. hacks.
Loading order could be:

1. full name
2. 3 letters
3. 2 letters
   Also useful for issue [Boxart] preview of boxarts during scrolling #73

How to solve the problem

No response

Describe alternatives you've considered

No response

Additional context

https://github.com/Polprzewodnikowy/N64FlashcartMenu/blob/main/src/menu/components/boxart.c#L24-L35