Add Notifications for Sign Up events

See the umbrella Jira for this issue:

The Sign Up tool should generate notifications when there are new events available for sign-up, or as reminders about events that a user has signed up for.

When you create a new event in Sign Up, you specify a date/time when signup for the event begins. This date should be used to generate a notification letting students know that they can begin signing up for that item.

Also, the Sign Up tool sends out a number of different email notifications and reminders for upcoming events once you sign up for something. We should add Notifications within the browser, so that it isn’t reliant only upon email notifications.

See the screenshot below of the current Sign Up settings related to notifications highlighted in yellow. I’d like to see browser notifications added anywhere that there is an existing email notification option.