Hey Brett! I think I found a crashing bug in Marked.

I have written a preprocessor script that takes two positional arguments. The first is a general string, and the second I am treating like a boolean flag. "true" and "yes" evaluate to true, otherwise false. Here's an example .md file (this version does not crash):

<!--
Custom Preprocessor: [true, "html", "true"]
-->

# A header

Some body.

The problem arises if I'm sloppy with quotes in the arguments. Nearly every combination of quoted and unquoted arguments works fine, but if I have the first positional argument quoted, but either the values true or false unquoted as the second argument, Marked crashes. e.g.:

Custom Preprocessor: [true, "html", true]

I'm probably taking liberties with JSON that are inappropriate, but nevertheless this is probably an exception worth catching rather than letting Marked simply crash, yes?

Thanks as always for a great app!