Write a howto-contribute.adoc

[henriette-einstein]

Write a Howto document that describes how to contribute to this project.

It should contain:

• A description of the versioning schema used by the project
• A description of how to write issues for the project
• A description of how to fork the project and create a pull request
• A description of the how to write commit messages according to the conventional commit syntax (https://www.conventionalcommits.org)
• A description of how to write test cases
• A description of how to create and publish a release