Add flashcards script

[RibbonUltra]

PR Title

A Python-based GUI Flashcard application

Summary

I want to add a Python-based GUI Flashcard application that helps users study.

Description

• Learning Mode: Study new cards.
• Review Mode: Review cards based on optimal memory intervals.
• Persistence: Auto-saves progress to a local JSON file.
• GUI: Built with Tkinter.

Closes #523

Checks

in the repository

• Made no changes that degrades the functioning of the repository
• Gave each commit a better title (unlike updated README.md)

in the PR

• Followed the format of the pull_request_template
• Made the Pull Request in a small level (for the creator's wellfare)
• Tested the changes you made

Thank You,

RibbonUltra

[yooung1]

Good project mate, I would suggest you to separate the UI and what the user will use, i'll be easier to mantain, you can create another file with the all the Tkinter and another class just for the user.