Add sort functionality to TaskList based on description or time

Add sort functionality to TaskList based on description or time

Add user guide

Fix code style issues

Refactor code to use Java streams

Personalise UI

Current UI is bland.

A more personalised UI will differentiate the app from others.

Let's,
- Change background color of Scene and DialogBox
- Change icon shape to be circle
- Change border color
- Change text color to suit background color
- Change width of scene

Personalise UI

Current UI is bland.

A more personalised UI will differentiate the app from others.

Let's,
- Change background color of Scene and DialogBox
- Change icon shape to be circle
- Change border color
- Change text color to suit background color
- Change width of scene

Refactor code to improve code quality

Set up CI

Allow GUI to be resizeable