feat: 优化代码，更新README

scripts/autoload/DownloadManager.gd

@@ -110,7 +110,6 @@ func load_resource():
 func get_sources():
 	var dir = DirAccess.open("user://download/")
 	var subdirs: PackedStringArray = dir.get_directories()
-	print(subdirs)
 	for subdir in subdirs:
 		if subdir == "temp":
 			continue

scripts/settings/settings.gd

@@ -12,9 +12,8 @@ func init_text() -> void:
 
 func init_sources() -> void:
 	DownloadManager.get_sources()
-	var options = $LoadSource/ChooseSource
 	for source_name in GameManager.sources:
-		options.add_item(source_name)
+		$LoadSource/ChooseSource.add_item(source_name)
 
 func _on_save_button_pressed() -> void:
 	GameManager.data_origin = $DataSetting/LineEdit.text