Client-side alerts

[morganney]

Need client-side alerts for scheduled stops. Not sure on the best UX. Allow the user to select a particular scheduled stop (by calling the umo schedules api) and then configure alerts for its impending arrival. Perhaps start with one time option of like 10 minutes before the predicted arrival.

Biggest questions are best UX for selecting/configuring the alert, and the options for notification or whether there should be more than one. Possible implementation could be web worker with notifications api.

Note, this is specifically client-side only in that these do not persist after the browser/app is closed, nor do they work across devices or time. However, if the PWA is "installed" as an app and the device has it running in the background, the alert should still function.

Alerts that are repeatable, or persist across devices and sessions, i.e. have backend support are a later feature...