docs: translate README.md to Portuguese (pt-BR)

Complete translation of README.md including:
- Main sections and headers
- Code examples with Portuguese variable names and comments
- Error messages and console logs
- Configuration descriptions
- All documentation links

Changes made:
✅ Translated all text to Brazilian Portuguese
✅ Updated code examples with Portuguese naming:
  - 'company' → 'empresa'
  - 'invoice' → 'notaFiscal'
  - 'issueInvoice()' → 'emitirNotaFiscal()'
  - Error messages in Portuguese
  - Console.log messages in Portuguese
✅ Updated email examples: .com → .com.br
✅ Maintained all technical terms (TypeScript, API, SDK, etc.)
✅ Kept code structure and functionality intact
✅ Updated section anchors to Portuguese

This improves accessibility for Brazilian developers using the SDK.

Author: andrekutianski