Create Week 3 A-Jar release

This is the first version!

Please run Duke.java with command

You can assume the user will run the jar file in the following way only:
https://nus-cs2103-ay2324s2.github.io/website/schedule/week3/project.html

Copy the jar file into an empty folder.
Open a command window in that folder.
Run the command java -jar {filename}.jar e.g., java -jar Duke.jar (i.e., run the command in the same folder as the jar file).