produce stub files

[famosab]

PR checklist

Closes #5492

• [ ] This comment contains a description of changes (with reason).
• [ ] If you've fixed a bug or added code that should be tested, add tests!
• [ ] If you've added a new tool - have you followed the module conventions in the contribution docs
• [ ] If necessary, include test data in your PR.
• [ ] Remove all TODO statements.
• [ ] Emit the versions.yml file.
• [ ] Follow the naming conventions.
• [ ] Follow the parameters requirements.
• [ ] Follow the input/output options guidelines.
• [ ] Add a resource label
• [ ] Use BioConda and BioContainers if possible to fulfil software requirements.
• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • For modules:
  • [ ] nf-core modules test <MODULE> --profile docker
  • [ ] nf-core modules test <MODULE> --profile singularity
  • [ ] nf-core modules test <MODULE> --profile conda
  • For subworkflows:
  • [ ] nf-core subworkflows test <SUBWORKFLOW> --profile docker
  • [ ] nf-core subworkflows test <SUBWORKFLOW> --profile singularity
  • [ ] nf-core subworkflows test <SUBWORKFLOW> --profile conda