Preserve book/label

[AndreaM2429]

Hi there! I implemented a new feature that I'd like to merge into the develop branch.
Thanks in advance for the feedback and the time to review my code.

Milestones:

• All data from Book and Label classes should be preserved by saving collections in .json files.
• The app is working as expected
• Menu options were modified

[CesarHerr]

Hi @AndreaM2429 ,

STATUS: APPROVED! 🥇 💯

Your project is complete! There is nothing else to say other than... it's time to merge it

Highlights

• Great job Preserving data 👍
• All linters passed ✔️

Optional suggestions

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

Good luck! 🎉

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

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