Add support for tectonic-typesetting

Tectonic is a modernized, complete, self-contained TeX/LaTeX engine, powered by XeTeX and TeXLive.

What’s in it for me?

• Tectonic automatically downloads support files so you don’t have to install a full LaTeX system in order to start using it. If you start using a new LaTeX package, Tectonic just pulls down the files it needs and continues processing. The underyling “bundle” technology allows for completely reproducible document compiles. Thanks to JFrog Bintray for hosting the large LaTeX resource files!
• Tectonic has sophisticated logic and automatically loops TeX and BibTeX as needed, and only as much as needed. In its default mode it doesn’t write TeX’s intermediate files and always produces a fully-processed document.
• The tectonic command-line program is quiet and never stops to ask for input.
• Thanks to the power of XeTeX, Tectonic can use modern OpenType fonts and is fully Unicode-enabled.
• The Tectonic engine has been extracted into a completely self-contained library so that it can be embedded in other applications.
• Tectonic has been forked from the old-fashioned WEB2C implementation of TeX and is developed in the open on GitHub using modern tools like the Rust language.

No files, tests, or entry points are named. Start by reviewing Scribble’s existing typesetting integrations and the Tectonic command-line or library interface, then define the integration scope and tests needed to show that documents compile successfully with Tectonic.