Add Service Worker & Push Notifications for critical points

[tienne-B]

As a method of notifying participants quicker than by email, a public service worker could broadcast current information once published to the participants. This could potentially reduce the number of requests sent to Tabbycat if pages are updated with the published details automatically.

There are some times for which a notification to participants may be warranted:

• Draw released
• Motion released
• Debates start

If possible, the service worker could also update the draw table in real-time. Notifications could be activated by participants on their first access to their private URL page, and thereafter the notifications could be filtered to just their draw, giving a notification like "You are debating %(side)s in room %(room)s" leading to the private URL page.

• https://developers.google.com/web/fundamentals/primers/service-workers
• https://developers.google.com/web/fundamentals/push-notifications

[tienne-B]

Some notes I have heard on the task:

• Participants at tournaments normally have all these events announced live (auditorium, Discord, etc.)
• Should participants be relying on their devices to get such information; notifications may be unreliable.