Update configuration schema to reflect that we expect an array of BibTeX file names.
Update configuration schema to reflect that we expect an array of BibTeX file names.

mangecoeur/autocomplete-bibtex,apcshields/autocomplete-bibtex,tpoisot/autocomplete-bibtex,lodestone/autocomplete-bibtex,tpoisot/autocomplete-citeproc,mdlincoln/autocomplete-bibtex