Support pandoc style citations

[savente93]

Pandoc is quite a popular utility and as such I assume that the in text citation styles are somewhat well known, so it would be good to support this as well. It will need to come with some way to configure this. Depending on how big the API gets I might have to look into possibilities for a config format.

https://pandoc.org/chunkedhtml-demo/8.20-citation-syntax.html