on provided prg/chr rom input args for dumping. Mirroring is sensed &
entered for fixed mirror mappers. So this is basic iNES file format.
Still don't have automatic banktable locating, nor mapper detection.
But this provides a basic header that should work with most currently
supported NES mappers. If the headers need tweaked, I recommend opening
in Mesen and using it's header modifcation tool.
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