[Feature Request] Change held button to open configuration menu on boot

[Tristan-Brulotte]

In order to allow systems (such as mine) with broken select buttons to boot outside of safe mode, or as a quality of life feature just for personal preference, it should be possible to modify the button which is to be held to open the configuration menu. This would be done through editing lines 257 and 271 in arm9/source/main.c and adding a new option to the Rosalina Menu.