Add dismissable hints to various timelines in web UI (#19315)

Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

app/javascript/mastodon/settings.js

@@ -45,3 +45,4 @@ export default class Settings {
 
 export const pushNotificationsSetting = new Settings('mastodon_push_notification_data');
 export const tagHistory = new Settings('mastodon_tag_history');
+export const bannerSettings = new Settings('mastodon_banner_settings');