tinytex 0.61

• The bib_engine argument of latexmk() now defaults to NULL, in which case the bibliography engine is inferred from the auxiliary files generated during compilation: if a .bcf file is found (produced by biblatex with the biber backend), biber is used, otherwise bibtex. Previously the default was always bibtex, so the bibliography of a biblatex + biber document was silently not built unless you set bib_engine = 'biber' or the global option tinytex.bib_engine (thanks, @HughParsonage, #19).