CodeMeta Data: Authors/contributors?

The following discussion from !3101 (merged) should be addressed:

• @bernd started a discussion: (+5 comments)

  The most relevant open questions concern authorship. CodeMeta distinguishes between "authors" and "contributors". Should we also distinguish? Who will be included? (How) do we automate the update of the file?

Add generic author (Dumux development team / Dumux developers) and list of contributors