LaTeX does not work on mobile

[Lars Quentin]

Describe the bug
Since the Android and iOS version do not have a LaTeX-Compiler installed, they cannot build LaTeX formulas.
This is intended by Anki. The normal workflow is that, once viewed in the Desktop client, the png gets rendered. Since we create the apkg outside of Anki, this is not a given in our case.

I also propose that we do not have a full dependency on a LaTeX distribution as it would insanely blow up the binary size.

To Reproduce
lol

Expected behavior
I would create a new parameter for generating the pngs. Then, one has to

• either have pdflatex and convert in their $PATH or
• Provide a link to those as well
  Dunno yet which one is better.

Desktop (please complete the following information):

• OS: Mobile
• Rust Version: any
• Anki Version: any