Notification Beta: restore `open-all-notifications` #3013

in Issues and in Pull Request there is a "Open Selected" function i like to have it also at the notifications beta

Example URL: https://github.com/notifications/beta?after=Y3Vyc29yOjUw&query=repo%3Agatsbyjs%2Fgatsby+is%3Aunread+is%3Apr+is%3Aclosed