Problem

I don't use Texlive, I useTectonic, and I usingplt.rcParams['text.usetex'] requires me to download a different LaTeX engine, not only because thelatex binary is searched, but also because thetex files that are meant for compilation are meant forpdflatex, and notxetex, which tectonic essentially wraps.

Proposed solution

Add a new option torcParams which will enable using a different LaTeX engine, and another option that will control whether the generatedtex files should be intended for xetex orpdftex.

This seems not too complicated to solve, but I wish to know what do you think, and whether you'd be willing to add more moving parts toTexManager class, especially since the generated tex files for axetex engine should be substantially different.