Harmonise repository structures and CONTRIBUTING.md

[Ludee]

The quality of the repo structures is fluctuating. Update and harmonise all repos.

Good examples: https://github.com/OpenEnergyPlatform/ontology/blob/dev/CONTRIBUTING.md

Bad examples: https://github.com/OpenEnergyPlatform/data-preprocessing

• [ ] Harmonise README.MD
• [ ] Harmonise CONTRIBUTING.md files https://github.com/OpenEnergyPlatform/organisation/issues/28
• [ ] Harmonise licenses
• [ ] Harmonise badges https://github.com/OpenEnergyPlatform/organisation/issues/46
• [ ] Add CITATION.cff
• [ ] requirements.txt or other requirements/dependency management to manage the dependencies (if the repository contains code that depends on packages)
• [ ] Harmonise milestones https://github.com/OpenEnergyPlatform/organisation/issues/5
• [ ] Harmonise Tags
• [ ] Harmonise GitHub projects
• [ ] Develop decision making
• [ ] Code of Conduct

[Ludee]

I came across this page for creating a good README.MD: https://github.com/18F/open-source-guide/blob/18f-pages/pages/making-readmes-readable.md