Add citation file

Summary: Added a first version of a citation file to MITK, based on https://citation-file-format.github.io/cff-initializer-javascript/#/

Test Plan: Look at the file, verify information, comment any mistakes / suggestions

Reviewers: O3 MITK Reviewer Group II, floca

Reviewed By: O3 MITK Reviewer Group II, floca

Subscribers: kislinsk, floca

Maniphest Tasks: T29446

Differential Revision: https://phabricator.mitk.org/D772