Support list loading

AssetStudioGUI/AssetStudioGUIForm.cs

@@ -166,6 +166,10 @@ namespace AssetStudioGUI
                 }
                 else
                 {
+                    if (paths.Length == 1 && File.Exists(paths[0]) && Path.GetExtension(paths[0]) == ".txt")
+                    {
+                        paths = File.ReadAllLines(paths[0]);
+                    }
                     await Task.Run(() => assetsManager.LoadFiles(paths));
                 }
                 BuildAssetStructures();