add download link to current presentation toast

...on-html5/imports/ui/components/presentation/component.jsx

...tton-html5/imports/ui/components/presentation/styles.scss

...html5/imports/ui/components/status-notifier/component.jsx

...n-html5/imports/ui/components/status-notifier/styles.scss

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

...on-html5/imports/ui/stylesheets/variables/typography.scss

bigbluebutton-html5/private/locales/en.json