As a person using the @dwyl app to track my time spent on activities/tasks,
I would like to receive a notification informing me that:

• The timer on my current activity has exceeded the original estimate

Before we implement Chrome (Browser) Push Notifications,
we need to document how it's done. (Document Driven Development!)
GOTO: dwyl/learn-push-notifications#1

When we start work on "Team Mode" #219 additional notifications need to be sent:

• A member of your team/community has requested your help on a task.
• A Task assigned to someone else has been marked as "ready for review"