Restructuring JavaScript into modules

[MattGomb]

In this pull request I:

• Split up the original JavaScript file into modules: book initialization, local storage, and user interface
• Added the required luxon-file for the current time and date
• Adjusted the CSS a little bit

[Omar-Muhamad]

Approved ✔

Hi @MattGomb,

Great job, Your project is complete! There is nothing else to say other than... it's time to merge it
Congratulations! 🎉

(Highlights) Good Points: 👍

• You documented your work professionally. ✔
• Github flow is used correctly. ✔
• All linters checks are ok. ✔

(Changes Required) Aspects to improve: ♻️

• N/A

[Optional] suggestions:

• N/A

Every comment with the [OPTIONAL] prefix is not crucial enough to stop the approval of this PR. However, I strongly recommend you to take them into account as they can make your code better.

**Cheers and Happy coding!👏👏👏

Feel free to leave any questions or comments in the PR thread if something is not 100% clear, and please remember to tag me in your question so I can receive the notification**

Please, do not open a new Pull Request for re-reviews. You should use the same Pull Request submitted for the first review, either valid or invalid unless it is requested otherwise.

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