Multiple docker tags per LateX engine

[qdm12]

The current image uses the pdftex engine

Make another image with for example the XeLaTeX engine.

Alternatively add instructions in the readme to setup a different typesetting engine.

[Skrallexxx]

Is there any sign of the container being able to use a different typesetting engine, ie. XeLaTeX?

[qdm12]

Sorry I don't really have the time, but I'll eventually get to it. Feel free to open a PR for a Dockerfile and I can finish up the CI part if you want.