Update user guide on README.md

Update Storage Parser to create Whisper.txt

Add title to window bar

Add HelpCommand for in-App guidance

Introduce a new HelpCommand class to provide users with in-App guidance.
The HelpCommand displays a help message to assist users in using the
application effectively.

Additionally, the Ui class has been updated to include a method for
printing the help message. The Parser class has also been modified to
recognize the "help" command and return the corresponding HelpCommand.

This enhancement improves the user experience by offering convenient
access to helpful information within the application.

Add dependencies for fxml

Refactor code to utilise Java Streams in ListCommand

In ListCommand class, utilise `forEach` with a method reference to
iterate over tasks and print each task using the `printTask` method of
the `Ui` class.

The changes leverage Java Streams to make the code more concise and
potentially improve readability. The modifications maintain the
functionality of the commands while adopting a more modern and
expressive coding style.

Add assertions to note important assumptions

In Whisper class, assertion is added to check validity of assumptions
regarding the initialisation of Ui, Storage, and TaskList.

In the Parser class, included assertions to verify assumptions about the
input parsing logic and command creation.

In the Command interface and implementing classes, used assertion to
ensure that critical conditions are met during command execution.

These assertions serve as documentation for developers and help in
identifying potential issues during development or maintenance.

Examines the code and refactor code.

This allows to improve the code quality based on the 'Code Quality' topic, and maximise readabilty.

Codes were being structured properly in for the import statements.

Separating the imports according to their packages is easier to see and checking purpose.

Add assertions to note important assumptions

In Whisper class, assertion is added to check validity of assumptions
regarding the initialisation of Ui, Storage, and TaskList.

In the Parser class, included assertions to verify assumptions about the
input parsing logic and command creation.

In the Command interface and implementing classes, used assertion to
ensure that critical conditions are met during command execution.

These assertions serve as documentation for developers and help in
identifying potential issues during development or maintenance.

Add javadoc to methods and class