Add licensing information

Currently, it is planned to license data, written content under a CC-BY-4.0 and code under the MIT license.

I will add the information to the repository according to the REUSE recommendations.

Nevertheless, one question is open.

❓ Whom do we make the copyright holder of the projects? HIFIS is not a legal entity, thus it cannot act as the copyright holder. So the question is, do we mention one center, multiple centers and if so, which?