Task: Add our commit strategy into the CONTRIBUTING.md

[linxpinx]

Goal

Our new Commit Strategy is to add a new commit for every Review. We want to have our commit strategy documented.

Acceptance Criteria

• [ ] the strategy is documented

Additional Information

In some other open source projekts on GitHub that Oli maintains, the policy is to add new commits after a review to make it more visible (and easier to review) what has changes. In these projects, the PR setting is to allow squash merging only. (The policy still is to have only 1 commit per review iteration, using squashing/amending.)