Improve research citations throughout

[frankelavsky]

1. We need to do a pass of all the research we've cited and update, remove, or clarify ones that don't make sense.
2. In addition, it might be helpful to put the title and authors of the research (like a real citation) and not just a link/doi to a publicly viewable paper.
3. We may also want to clarify how a given research paper supports the heuristic (for example, some papers might really just recommend a practice but don't methodologically prove something or even relate to accessibility at all).

Background:
Our version 2 update included significant changes and feedback from the community, improving the wording, explanations, and organization of many of our heuristics. However, we didn't do a thorough check of whether the cited research still technically relates to the newest version of each test. Some references might need to be removed, argued, or we might need to cite additional work.

In particular, a researcher in the community mentioned in conversation that we are citing Borkin's Beyond Memorability paper https://ieeexplore.ieee.org/document/7192646, which we currently cite in our "Needs a title" criteria. This paper has strong evidence that titles are important in various ways, but requiring them for accessibility reasons isn't what the paper is about. We want to be sure we clarify what a paper says and how we have interpreted that.