Follow-up from "Feat: Introducing JSON-LD and refactoring code-base"

The following discussion from !45 (merged) should be addressed:

• @schaefer49 started a discussion: (+1 comment)

  This could be changed to “2022-2025 Georg-August-Universität Göttingen” everywhere, see https://spdx.github.io/spdx-spec/v2.3/file-tags/.

Let's update the copyright header using reuse.