Add Brazilian Portuguese version of the .NET Interview Questions

[rodri-oliveira-dev]

This PR introduces a Brazilian Portuguese (pt-BR) version of the .NET Interview Questions project.

The goal is not only to translate the original material, but also to make it accessible to Portuguese-speaking .NET developers while preserving the original project's purpose and structure.

What was included

• Brazilian Portuguese translation of the available interview content
• Technical and terminology review of the .NET and C# questions
• Review and modernization of outdated explanations where necessary
• 20 Array questions
• 20 List<T> questions
• 20 Tree questions
• 50 general .NET/C# questions
• 20 SQL questions
• .NET 10 solution for validating the code examples
• GitHub Actions workflow for restore and build validation
• Smoke tests for the executable examples
• Compilation warnings treated as errors

In total, 130 interview questions and exercises were reviewed and made available in Brazilian Portuguese.

The intention is to help make this excellent resource accessible to a larger part of the .NET community.

I kept the original project as the reference and attribution for this work.

If you prefer a different structure for hosting translations, such as a dedicated pt-BR directory or simply referencing the translated repository from the main README, I would be happy to adapt the contribution accordingly.

Thank you for creating and maintaining this project!