Include a Contributing.md to help newcomers to contribute

For newcomers, it is hard to make their first contribution. Well-Written contributing guidelines can describe the workflow of the projects, and where to start for newcomers, which could help them onboarding much easier.

Start by reviewing the repository structure and any existing contribution guidance before creating Contributing.md. Document the project workflow and beginner starting points described by the issue; the work is done when newcomers have a clear contribution guide in that file.

Written by the indexing model from the issue text.