ScummVM and Numero cores added

New cores added for RetroArch Steam.

https://store.steampowered.com/app/2301080/RetroArch__Numero/

https://store.steampowered.com/app/2345800/RetroArch__ScummVM/

You can download these cores either from within RetroArch Steam by going to Manage Cores, or by simply downloading it for free from Steam.

There are now 57 cores available in total for RetroArch Steam.