Standardizing the 100-word preview summaries displayed in study grid

[msheskin]

Researchers have many different approaches to writing the "under 100 words" preview summary that appears on the listing page of available studies. That is a field that was added more recently than the "short description" and "purpose" fields, and we have not updated instructions, self-review checklists, or admin review to reflect it.

Thus, researchers have chosen a lot of different approaches. For example, they have different mixes of "what" and "purpose". And some just say "This study will take place on a video call, live with a researcher!" and nothing more. And there are many more variations!

For some useful standardization, one idea is that we require the following template (exceptions allowable for good reasons):
[optional detail about study delivery] + [major detail about what happens] + [optional major detail about purpose]

Below is what it would look like for a few examples. In each example, both optional bits are included, but some studies might not have anything to include in the first bit (especially if it was just a "standard" internal study):

• "In this scheduled video chat with a researcher, your baby will look at pictures of orange and blue shapes, and we will learn how babies understand numbers."
• "In this study that requires your child to have paper and crayons, your child will draw pictures of imaginary objects, and we will learn about children's artistic preferences."
• In this study that involves at least one scheduled session and might include up to four more, your child will chat with a researcher about science demonstrations, and we will learn about children's memory abilities

This should be updated in multiple places:

• Admin review document (Mark can do this, once we decide on content, such as the above suggestion)
• The read the docs entry for "Preview summary" here
• The self-review checkist should mention this

[becky-gilbert]

Thanks @msheskin, I can take care of this one too following approval/comments from @mekline.