add a small style for toast notification and add a content prop in toast

...ml5/imports/ui/components/chat/notification/component.jsx

...ponents/chat/notification/push-notification/component.jsx

bigbluebutton-html5/imports/ui/components/chat/styles.scss

...luebutton-html5/imports/ui/components/toast/component.jsx

bigbluebutton-html5/imports/ui/components/toast/styles.scss

...luebutton-html5/imports/ui/services/notification/index.js

bigbluebutton-html5/private/config/settings-development.json

bigbluebutton-html5/private/config/settings-production.json

bigbluebutton-html5/private/locales/en.json