STRUCTURE - Add new Experiment Runner config docs

[okaycj]

We have plans on moving the experiment runner config to its own view. This should be documented as well as updating the documentation around study edit/creation.

[becky-gilbert]

I think this is the same issue as the "split form" issue here: #327

We split the old "study create/edit" form into (1) study details, which are not specific to study type, and (2) study-type-specific fields, including experiment runner info. I think this issue was about updating the docs with the experiment runner config fields in their own form - if so, then this issue can be closed as a duplicate.