Add Northern Lights theme

Overview

This pull request adds the Northern Lights theme to the project, providing users with a visually stunning option for customizing the application's appearance. The Northern Lights theme incorporates a beautiful combination of exciting colors and smooth transitions resembling the Aurora Borealis phenomenon, enhancing the overall user experience.

Details

In this branch, I have implemented the following changes:

Updated the settings.json file and added a new JSON document for the Northern Lights Theme
Updated the application's configuration to include the Northern Lights theme as an available option.

Testing

To ensure the quality and compatibility of the Northern Lights theme, I have tested this new theme on multiple IDEs.

Dependencies

This pull request does not introduce any new dependencies or require any additional configurations. It is designed to seamlessly integrate with the existing codebase and can be easily deployed without any special setup requirements.

Additional Notes

The Northern Lights theme is intended to provide a visually appealing option while maintaining the application's performance and accessibility standards.
I have paid attention to code organization and have followed best practices to ensure maintainability and extensibility.
The theme selector UI has been updated to include the Northern Lights theme as a selectable option.

Please review this pull request and let me know if you have any feedback or suggestions for improvement. I believe that the Northern Lights theme will greatly enhance the user experience and contribute to the overall aesthetics of the application. Thank you!

matheusfelipeog / calculadora-tk