Add module GHA docs

[sjspielman]

This issue tracks adding a docs page to the new ensuring-repro/analysis-module-workflows section (see #494) that explains the module testing GHAs. Here are some thoughts for the content we should include here:

• All modules have a workflow which gets run upon changes to that module and periodically as cron. To begin it will use renv/conda to manage the environment but as the analysis matures, we'd like for it to use the docker file (note the timing of when to file such changes, link to docker section)
• An inactivated workflow created when you created your module (link)
• We should provide some brief details on how to write/update a workflow:
  • GHAs should use test data and can call the module shell script (link).
• Explain when the workflow is run

[sjspielman]

Closed by #528