[Doc] - Add product screenshot and user guide

Author: joel-lim

docs/README.md

@@ -2,19 +2,153 @@
 
 ## Features 
 
-### Feature 1 
-Description of feature.
+### Check off your tasks
+Duke provides the functionality of a to-do list with 3 built-in task types: Todos, Deadlines and Events.
+Once you are done with a task, you can mark it as complete and Duke will remember its completion status.
+
+### Search for related tasks
+If your task list is simply too long, Duke allows you to streamline your search for related tasks by keyword.
+
+### Reschedule tasks
+A deadline changed, or you made a typo? Fret not! Duke lets you reschedule your tasks with one easy command.
 
 ## Usage
 
-### `Keyword` - Describe action
+### `Keyword` - todo
+
+Create a Todo task with a given description.
+
+Example of usage: 
+
+`todo 2103 IP`
+
+Expected outcome:
+
+`Got it. I've added this task:`
+`  [T][✘] 2103 IP`
+`Now you have x tasks in the list.`
+
+### `Keyword` - deadline
+
+Create a Deadline task with a given description as well as due date.
+
+Example of usage: 
+
+`Usage: deadline 2103 IP submission /by 24-02-2020`
+
+Expected outcome:
+
+`Got it. I've added this task:`
+`  [D][✘] 2103 IP submission (by: Feb 24 2020, 00:00)`
+`Now you have 2 tasks in the list.`
+
+### `Keyword` - event
+
+Create an Event task with a given description, start and end time.
+
+Example of usage: 
+
+`Usage: event 2103 tutorial /at 19/02/2020 12:00 to 19/02/2020 13:00`
+
+Expected outcome:
+
+`Got it. I've added this task:`
+`  [E][✘] 2103 tutorial (at: Feb 19 2020, 12:00 to Feb 19 2020, 13:00)`
+`Now you have 3 tasks in the list.`
+
+### `Keyword` - done
+
+Mark a task as complete.
+
+Example of usage: 
+
+`done 1`
+
+Expected outcome:
+
+`Nice! I've marked this task as done:`
+`  [T][✓] 2103 IP`
+
+### `Keyword` - done
+
+Mark a task as complete by index.
+
+Example of usage: 
+
+`done 1`
+
+Expected outcome:
+
+`Nice! I've marked this task as done:`
+`  [T][✓] 2103 IP`
+
+### `Keyword` - list
+
+List all tasks.
+
+Example of usage: 
+
+`list`
+
+Expected outcome:
+
+`Here are the tasks in your list:`
+`1.[T][✓] 2103 IP`
+`2.[D][✘] 2103 IP submission (by: Feb 24 2020, 00:00)`
+`3.[E][✘] 2103 tutorial (at: Feb 19 2020, 12:00 to Feb 19 2020, 13:00)`
 
-Describe action and its outcome.
+### `Keyword` - delete
+
+Delete a task by index.
+
+Example of usage: 
+
+`delete 3`
+
+Expected outcome:
+
+`Noted. I've removed this task:`
+`  [E][✘] 2103 tutorial (at: Feb 19 2020, 12:00 to Feb 19 2020, 13:00)`
+`Now you have 2 tasks in the list.`
+
+### `Keyword` - find
+
+Search for related tasks by keyword.
 
 Example of usage: 
 
-`keyword (optional arguments)`
+`find submission`
 
 Expected outcome:
 
-`outcome`
+`Here are the matching tasks in your list:`
+`1.[D][✘] 2103 IP submission (by: Feb 24 2020, 00:00)`
+
+### `Keyword` - reschedule
+
+Reschedule a task by index (Deadline or Event).
+
+Example of usage: 
+
+`reschedule 2 25/12/2020`
+
+Expected outcome:
+
+`I've rescheduled this task:`
+`  [D][✘] 2103 IP submission (by: Dec 25 2020, 00:00)`
+
+### `Keyword` - bye
+
+Exit Duke.
+
+Example of usage: 
+
+`bye`
+
+Expected outcome:
+
+`Save Success! See you next time!`
+
+
+
+