docs: add comprehensive CONTRIBUTING.md and update README

- Create CONTRIBUTING.md with complete contributor guidelines
- Document development setup, environment, and tooling
- Include code style guide with TypeScript conventions
- Provide detailed testing requirements and examples
- Document git workflow, branch naming, and commit message format
- Explain PR process with templates and expectations
- Include code review guidelines and policies
- Add reference to CONTRIBUTING.md in README Links section
- Add Contributing section to README with quick reference

Signed-off-by: leocavalcante <leo@cavalcante.dev>

Author: leocavalcante