Level-5

Add error handling

Add error handling for two specific cases

Level-4

Add task type

Tasks do not have a type, making it hard to tell what is the nature of the task

Add types to differentiate between different types of task

Level-3

Add Marking

Tasks cannot be marked as done or not done yet.

Add functionality for marking and unmarking

Level-2

Add Add and List Functionality

Level-1

Update Duke.java

Add echo for commands