[Feature Request] Boot from CD

Add option to load a mounted disc drive instead of just disc image files.

Saturn discs are readable by any standard CD-ROM drive so it would be a reasonable option to be able to boot a game disc directly instead of having to waste time and storage space running an external tool to dump it.

This is also a pretty standard emulator feature, the most prominent emulators for the other 2 major consoles that have standard unprotected discs (PS1, PS2) have this feature.