Add template or "annotation checklist" for users

[dwhly]

Moved from https://github.com/hypothesis/h/issues/1694

@anderspeders wrote there:

"I would like to offer a template or checklist to users, so that they will go through the document checking for each of the features (eg. check for a specific clause or the date of termination in a contract)."

We have also heard this request-- primarily from legal users wanting to be able to guide the annotation of case law and other similar documents, and from the scholarly communication world, for instance where an editor wants to ensure that reviewers submit an overall article level review that answers some basic questions, like whether the article is recommended for publication, and other key pieces of summary feedback that are template driven and should be collected and organized the same way for every review.