Write function to get CSL from styles repo

[Francisco Rodriguez-Sanchez]

So that one can just say
csl: get_csl("ecology-letters)
in YAML and this function will fetch that CSL style from the GitHub repo and save it in the directory of the Rmd document

[Francisco Rodriguez-Sanchez]

Apparently one can specify link to zotero styles repo directly, e.g.:

csl: https://www.zotero.org/styles/ecosistemas