Consider adding more context for citation formatting

Nobody has claimed this yet.

> One comment re: wording [for citation guidance] to perhaps consider: That we generally want to ask people to cite both software _and_ paper (if there is a paper) is an institutional practice we chose. But prioritizing the paper citation can also be a choice, which can result in actually _wanting_ the paper citation to show up on the sidebar on GitHub (and perhaps including the code citation BibTeX in the README instead).
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> I don't have a good suggestion for how to convey this being a choice when instantiating the template, and of course there are a variety of reasons why code as a first-class citizen in citation networks should be promoted. So maybe this is best deferred to considering at a later time.
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> _Originally posted by @hlapp in https://github.com/Imageomics/Collaborative-distributed-science-guide/pull/69#pullrequestreview-4189999222_

We may consider including more context in a collapsible box/admonition for those interested in deciding between the two options. The preferred option is still to have a code citation and ask for paper citation in the README.

Start by locating the citation guidance and its template in the guide, then read the surrounding wording and any existing admonition or collapsible-box conventions. Done means adding context for choosing between code and paper citations while preserving the stated preference for a code citation and requesting the paper citation in the README.

Written by the indexing model from the issue text.