Add StartupVideo asset type

ArchiSteamFarm/Steam/Data/Asset.cs

@@ -257,6 +257,7 @@ public sealed class Asset {
 		MiniProfileBackground,
 		AvatarProfileFrame,
 		AnimatedAvatar,
-		KeyboardSkin
+		KeyboardSkin,
+		StartupVideo,
 	}
 }

ArchiSteamFarm/Steam/Data/InventoryResponse.cs

@@ -197,6 +197,8 @@ internal sealed class InventoryResponse : OptionalResultResponse {
 									return Asset.EType.AnimatedAvatar;
 								case "item_class_16":
 									return Asset.EType.KeyboardSkin;
+								case "item_class_17":
+									return Asset.EType.StartupVideo;
 								default:
 									ASF.ArchiLogger.LogGenericError(string.Format(CultureInfo.CurrentCulture, Strings.WarningUnknownValuePleaseReport, nameof(tag.Value), tag.Value));