GameList: Show game mod descriptor .json files in game list.

Source/Core/DiscIO/Blob.cpp

@@ -50,6 +50,8 @@ std::string GetName(BlobType blob_type, bool translate)
     return "WIA";
   case BlobType::RVZ:
     return "RVZ";
+  case BlobType::MOD_DESCRIPTOR:
+    return translate_str("Mod");
   default:
     return "";
   }

Source/Core/DiscIO/Blob.h

@@ -39,6 +39,7 @@ enum class BlobType
   TGC,
   WIA,
   RVZ,
+  MOD_DESCRIPTOR,
 };
 
 std::string GetName(BlobType blob_type, bool translate);