[Feature Request] Detect NKIT file when loading ISO/WBFS, display relevant error message before processing with WIT

[mask1n]

^as per the title

From what I've seen, enough users in the Custom Street Discord have encountered error codes when WIT attempts to process the file that would be unclear to the end-user

In my opinion, this along with updated documentation to alert new users of CSMM/WIT's incompatibility with NKIT would be pretty helpful

[Sophilautia]

+1