Also reimplemented bye

did the OOP

This reverts commit ba7ef1a.

This reverts commit b7dff63.

Update to use getter for retrieving TaskList

Made modifications to several access modifiers, method names, enum values and exceptions returned.

mainClassName in the Gradle config is set to duke.Duke.

The current main class should be duke.Launcher instead.

The variable has thus been changed to duke.Launcher.

Some methods were missing assertions that could be useful for
developers.

Assertions could be used to make sure unexpected behaviour does not
occur during runtime.

Let's add assert statements to two segments of code:
* In Parser, an assert in getTaskName was added to ensure the input
array has more than one element, indicating a name is present
* In  TaskList, an assert in the constructor was added to ensure that
if the task parsed is a ToDo (msg.length == 1), that no date has been
parsed as expected.

Parser method is extensive with numerous duplicate code fragments.

Excessively long code is difficult to both read and debug.

Let's refactor code by extracting two methods:
* create parseDateTime to convert string into LocalDateTime
* create tokenizeInput to convert string into tokens with error
handling

Add assertions to important methods

Refactor parse method in Parser

There is no simple way to organize tasks in the task list.

Users who want to sort their tasks by upcoming deadline or alphabetical
order could not do so easily.

Let's add a sort command that allows users to sort the list either
alphabetically or chronologically, and in ascending or descending
order.

Let's also refactor the Task class to include time as well.

Let's add more JavaDoc comments to previously undocumented code.

Sort command only parses user input if it strictly matches the listed parameters.
Users need to type entire parameter, which is long and not user-friendly.

Let's check if user input matches the starting characters of the parameter instead of the whole string.

Error messages are undifferentiated from normal Duke messages.
Users may be unsure when they are getting error messages.

Let's add an error message dialog to better distinguish the two.

Let's update the user guide for a more user-friendly experience.

Remove duplicate entry for list in user guide.