Add another TeX math rendering engine : KaTeX

[fylimas]

I have just run into Piggydb for several days, and I wish I have got to know it several years earlier. Piggydb is working as exact what I was looking for. I have even written a bare app with go the last year, but that is still a long way from what I expected. Thank you very much for your creation.

I use piggydb to manage some knowledge points or notes when I am reading papers and books. And a lot of TeX math is involved. I certainly want the TeX math rendering engine works correctly and fast.

Piggydb is now using mathjax as the TeX math rendering engine.
However, a new rendering engine KaTeX developed by the Khan Academy.
The KaTeX renders TeX math much faster than mathjax, though KaTeX can still not handle as much type of expressions as mathjax.

So, I wonder if it is possible to add KaTeX as an additional rendering engine to finally enable the users to switch between the engines.