Banners display important, succinct messages. They can provide actions for the user to take. They requires user action to be dismissed.
Banners are persistent and non-modal, and they should be displayed at the top of the viewport, below a top app bar. Only one banner should be shown to the user at any time.
npm install --save-dev @smui/banner
https://sveltematerialui.com/demo/banner
See Banners in the Material design spec.
See Banner in MDC-Web for information about the upstream library's architecture.