Add content describing the process to become part of Reviewer of the Week

The idea is that the process for how we add reviewers to the "Reviewer of the Week" group should be transparent and well documented. (Related: https://github.com/wikipathways/academy/issues/39#issuecomment-1712578688)

Initial ideas from Curator's meeting:

Requirements / Skills ladder

1. Familiar with GitHub, at least the subset of tasks that reviewers will perform. We can provide link to existing external (generic) GitHub tutorials, but if we want some way of assessing familiarity, or more tailored training, we need to design something. Maybe a track in the Academy? At least for folks who just started with GitHub because of WP.
2. Experience/proficient with pathway drawing. Minimum of 1 original pathway model, maybe specifically from pathway-curation-task repo (or PFOCR subset)?
3. On boarding process: go through the needed steps with an experienced reviewer. The steps should be described either in a new Academy track (if it makes sense) or some other tutorial.
4. Have a sandbox repo and use it for new reviewers to do a trial run. Perhaps this can be used during onboarding.
5. Evaluate the first report of a new reviewer