Cleanup and add args

[mhmd-shadfar]

Hi,
First, I'd like to thank you for the amazing work you've done on this project. Your code has been incredibly helpful.

This pull request refactors the code to enhance scalability and accelerate future development.

changes:

1. clean up the code.
2. create utils.py and add get_background() and create_overlay() which you code but I put it in function so that the code looks much cleaner in the future, if you want to add other functions add them to this file.
3. put chars and numbers and nimi_numbers in the number_char_config.json file so that the main.py is cleaner and you can edit this JSON file in the future if needed.
4. add input arguments for output-dir and the number of samples.
5. edit .gitignore file
6. edit the readme file

Thank you again for your hard work and dedication to this project!

Best regards,
mohamad