Plink linkage disequilibrium additional output

[DavideBag]

PR checklist

Closes #5145

• [x] If you've fixed a bug or added code that should be tested, add tests!
• [x] If necessary, include test data in your PR.
• [x] Remove all TODO statements.
• [x] Emit the versions.yml file.
• [x] Follow the naming conventions.
• [x] Follow the parameters requirements.
• [x] Follow the input/output options guidelines.
• [x] Add a resource label
• [x] 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:
    • [x] nf-core modules test <MODULE> --profile docker
    • [ ] nf-core modules test <MODULE> --profile singularity
    • [ ] nf-core modules test <MODULE> --profile conda