CompatHelper: bump compat for NCDatasets to 0.12, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the NCDatasets package from 0.9, 0.10, 0.11 to 0.9, 0.10, 0.11, 0.12. This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry. It is your responsibility to make sure that your package tests pass before you merge this pull request.