Docs: Missing references in BibTex format in reference page.

[ojeda-e]

Expected behavior

In docs, the references should display citations following the BibTex format.

Note: This change was left on purpose given that PR #3663 was getting too large. (See comment)

Actual behavior

To fix this issue:

• [ ] Update package/doc/sphinx/source/documentation_pages/references.rst to citations with BibTex format.
• [ ] Update requirements to sphinx (with no pinned version, correct @IAlibay? See comment)

[orbeckst]

@ojeda-e , I created a Zotero group for references for MDAnalysis papers https://www.zotero.org/groups/4747225/ — currently for work on the MDAKits whitepaper but could be generally useful for paper writing.

Do you want to become a member of the group so that you can add papers, e.g., all the papers that you already bibified for your recent PRs? You can also upload the PDFs and use the group as cloud storage — it runs under my lab account with unlimited storage. If so, email me an email address or your zotero username or maybe there's a way to request membership on the zotero group page itself.