Add CONTRIBUTING guidelines #271
Description
User story
Add contributing guidelines for community developers: https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/setting-guidelines-for-repository-contributors .
Conditions of satisfaction
- An optional list of conditions that have to be fulfilled for this feature to be complete.
- For example: "Users can add both individual items and lists as parameters."
Acceptance tests
- An optional list of tests that should be written to automatically test the new feature.