docs: add portuguese translation

[CarlosZiegler]

Motivation and Context

This change improves accessibility for Portuguese-speaking developers by providing localized documentation.
It also establishes a dedicated docs/ folder to organize future translations and documentation enhancements.

How Has This Been Tested?

No runtime changes — documentation only.
Visual verification of file presence and content accuracy.

Breaking Changes

No breaking changes.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

• Created a docs/ folder to store translations
• First addition: README.pt-BR.md (Brazilian Portuguese translation)
• Maintains full structure and technical consistency with the original English README.

[ihrpr]

Thank you for contributing to SDK. Closing this PR as maintaining translations in the SDK repo without infrastructure would lead to outdated content and increased maintenance burden.