Create a simple streak counter
- A user should be able to add an activity.
- An activity should have a name, URL for an image and a start date
- A user should see all added activities.
- A user can view a single activity and see the duration of the streak.
- A user should see the streak with the longest duration.
- Use strong typing.
- Have 3 or more classes.
- Have at least one static method.
- Separate interfaces to separate files.