Improve Guide > Scholarly Writing > Citations page

[cwickham]

From discussion on quarto-dev/quarto-web#1209:

Probably a reorganization would be helpful. A simple one could be

• This pages is about Citations. We could bigger sub part to clearly explain the different system that could happen
• One about Pandoc's citeproc built in system. Almost all content of the current page would be under it
• One about Format specific system and
  • A subpart about LaTeX system
  • Another about typst own system
    The pandoc syntax could be at the top as a common part.