Rename AdvancedConfig.Extension to FileExtension

Data/RenderConfig.cs

@@ -26,7 +26,7 @@ namespace ADOFAIRenderer.Data
         public int? RandomSeed { get; set; } = null;
         public bool ProcessAudio { get; set; } = true;
         public bool NonTile { get; set; } = false;
-        public string Extension { get; set; } = "mkv";
+        public string FileExtension { get; set; } = "mkv";
     }
 
     public class VideoEncodingConfig