Docs request: Organizing your module results

### What is the documentation improvement or update you wish to see?

We should add recommendations about how contributors might consider structuring their results output. The reason for this is because of how we anticipate to port modules over to `OpenScPCA-nf`, and associated use of the `download-results.py` script which has the ability to take `projects` and `samples` arguments. This would likely be a new doc added somewhere in the analysis modules section.

In parallel to explaining this results file structure, we should document the `projects` and `samples` arguments in the results download script. This should be added directly to those existing docs (forthcoming in #428, but will exist once we're ready to tackle this issue).

### Is there any additional context you would like to provide?

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### If this request is for an existing documentation page, please provide the link here.

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Review the analysis modules documentation and the documentation for download-results.py after the work in #428 is available. Document recommended projects and samples result structure, then add the script's projects and samples arguments to its existing documentation; the issue is done when both documentation areas explain the expected layout and arguments.

Written by the indexing model from the issue text.