docs(README): Adding Contributors guide

[gorakhnathy7]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement
• [ ] Refactoring
• [ ] Dependency updates
• [X] Documentation
• [ ] CI/CD

Description

Additional Changes

• [ ] This PR modifies the API contract
• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

to close #5344

Motivation and Context

How did you test it?

Checklist

• [ ] I formatted the code cargo +nightly fmt --all
• [ ] I addressed lints thrown by cargo clippy
• [ ] I reviewed the submitted code
• [ ] I added unit tests for my changes where possible