Add LaTeX cheat sheet

[Daniel-Hug]

The markdown cheat sheet is super helpful, and I would find a LaTeX cheat sheet to be equally helpful.

[akerbos]

Maybe this guide we wrote for cs.SE can be a starting point.

[pkra]

Other suggestions:

• a concise one: http://www.haptonstahl.org/latex/basics_mathmode.php
• the big one: http://meta.math.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference and

[RoyiAvital]

That could be amazing.