Katex overflow

[JurajLieskovsky]

I set overflow: auto hidden for display equations as suggested here so that they do not overflow the page if they are too long and instead become scrollable. In the process I updated KaTeX to version 0.16.2.

Except katex.ccs which I edited, I copied over the minified versions of the remaining files without any changes, although I am not sure if the full versions wouldn't suffice as hugo itself has a minify option. But I am not familiar enough with it to make this decision so I keep the changes to a minimum.