Contributing guidelines

[ayushanand18]

Overview

This PR aims to add Contributor Guidelines on CONTRIBUTING.md to the pyobis project.

• It aims to resolve #19

Notes for Reviewers

Please review the Contributor Guidelines and highlight changes if I need to add some more points here.

Next Steps

I am now working on creating a PR for the usage_guide.ipynb file post this review.

[ayushanand18]

I have updated the contributing guide as per the changes suggested. I have also added some sections:

• why contribute to the open source?
• pyobis, and its aim
• additional suggestions
• further reading