Function showNotification

showNotification(msg, type, pid, ref, pos, off, dur, closable): void
Shows a notification popup.
Parameters
- msg: string
  message to show
- type: "warning" | "info" | "error"
  the notification type (warning, info, error)
- pid: string
  uuid of the page to which it belongs
- ref: Widget<HTMLElement>
  a reference component
- pos: string
  the position of notification
- off: Offset
  the offset of x and y
- dur: number
  the duration of notification
- closable: boolean
  the close button of notification
Returns void