Update user guide

data/data.txt

@@ -1,3 +1,4 @@
 D%d%false%d%flying%d%1829-12-23
-T%d%false%d%test
+T%d%true%d%test
 E%d%false%d%test%d%2020-12-12
+D%d%false%d%test%d%2020-12-12

docs/README.md

@@ -63,6 +63,18 @@ A deadline task of name `name` due by `<yyyy-mm-dd>` will be added
 
 Example of usage: `deadline CS2103 IP Submission /at <2025-10-29>` - adds a deadline task named "CS2103 IP Submission" due on 29th October 2025 to the list of tasks
 
+### `done <task index>` - **Mark a task as done**
+
+The task at the index indicated by the user will be marked as done.
+
+Example of usage: `done 2`
+
+### `delete <task index>` - **Delete a task**
+
+The task at the index indicated by the user will be deleted.
+
+Example of usage: `delete 7`
+
 ### `load` - **Choose a file to load/save to**
 
 Jarvis prompts the user for a .txt file to load from and save tasks to

src/main/java/InvalidInputException.java

@@ -1,5 +1,5 @@
 class InvalidInputException extends DukeException {
     public InvalidInputException() {
-        super("☹ OOPS!!! I'm sorry, but I don't know what that means :-(");
+        super("OOPS!!! I'm sorry, but I don't know what that means :-(");
     }
 }