此接口提供了与无障碍相关的方法和事件。
有时，在应用程序中宣布状态变化（例如，有新消息）非常重要，以便视力受损的用户能够意识到屏幕上发生了变化。可以对多个公告进行排队。
// Triggered when the high-contrast setting changes.
highContrastChangedEvent: SubscribableEvent<(isEnabled: boolean) => void>;
// Triggered when the screen reader setting changes.
screenReaderChangedEvent: SubscribableEvent<(isEnabled: boolean) => void>;
// Sends the specified string to the screen reader.
announceForAccessibility(announcement: string): void;
// Indicates whether a screen reader is currently enabled.
isScreenReaderEnabled(): boolean;
// Indicates whether the OS-level "high-contrast" setting is enabled.
isHighContrastEnabled(): boolean;