Meta-Issue: Tasks for getting Codemeta better

[ChristianTackeGSI]

(Copied from #1028 (comment) by @dennisklein)

Individual parts of this list can be handled in dedicated PRs or Issues.

I suggest to follow up on this by:

• Rebase on current dev branch
  • Add initial codemeta.json #1028
• Define the authoritative place for the version number
  a. Keep it in CMakeLists.txt or
  b. CMake queries version number from codemeta.json
  • Add the CMake code written by @ChristianTackeGSI that queries the version number from codemeta.json
• Adopt codemeta_update.py from FairMQ repo (in case of b probably can be stripped down to the author logic only)
  • docs: Use meta_update to update codemeta.json #1383
• Add a release checklist for maintainers so we do not forget to press this button from time to time
  • docs: Start on the Release Process #1319
• CI consistency check welcome too

Regarding the authoritative place for the version number, I personally have no preference whether to go with options a or b. @fuhlig1 @ChristianTackeGSI What is your preference?