[Feature] Pass firmware/bios files to muOS App if they exist on server

[Moonraka]

I was testing some supported consoles on my RG40XXV and I downloaded a SegaCD game and it created the correct folder under content but when I clicked the game it would not load, just a black screen and back to game list.

It seems it needs the bios files to play. I manually moved over my bios files to the correct folder and reloaded the game and it worked just fine.

Bios Location - /mnt/mmc/MUOS/bios
* Sega CD - Just drop into folder
* *Other consoles potentially under their own emulator (will share picture of my current setup)

Please let me know if you need anything else

[gantoine]

I've updated in /firmware endpoint in 3.8.1 to allow fetching all firmware (ie not having to pass a platform ID).