docs: include `CONTRIBUTING.md`

[alestiago]

Description

As a developer interested in contributing I would like to have a CONTRIBUTING.md file that outlines:

1. How to run the tool in my local environment
2. How the overall structure of the tool works (explained with correct visualisations)
3. Know on what features the team would like external contributors to work and how to create a correct pull request.

Requirements

• [ ] Include a CONTRIBUTING.md file
• [ ] Explain how the tool works internally (with visualisations)
• [ ] Include instructions on how to run the tool in my local environment (for MacOs, Windows and Linux)
• [ ] Include instructions on how to find features available for contribution or suggest features
• [ ] Include instructions on how to open a good pull request or issue