Godot Autoload

Autoload（singleton）必须是基础自node的script或者是packedscene

func add_autoload(name, resource):

    var node

    if resource is Script:

        node = resource.new()

    elif resource is PackedScene:

        node = resource.instance()

    else:

        return

    node.name = name

    get_tree().get_root().add_child(node)

    # node now exists at $/root/DialogueSystem