Syntax Highlighting and Preview problems with escaped Underscore and Asterisk characters.

[MatthewRaymond]

When using a backslash to escape an asterisk or underscore character ("*", "_"), the syntax highlighting ignores the backslash and processes the asterisk or underscore as the beginning their respective forms of emphasis. It also continues the italics or underline highlighting until it hits a second asterisk or underscore, which is incorrect. Emphasis like bold, italics and underline is not supposed to cross line breaks. A single asterisk or underscore on a line should be treated as that character, not a form of emphasis that continues until a second asterisk or underscore is found. The preview properly handles escaped underscores and asterisks correctly, but it doesn't properly handle the situation with a single asterisk or underscore on a line.

[superlou]

With respect to the preview, there's not much we can do since that's generated by Afterwriting, though we could open an issue in their project.

I confirmed that the grammar definitely isn't highlighting strictly per the Fountain emphasis rules. Unfortunately, the regex in there is a big mess. I'm going to look at untangling it, but it's unlikely to strictly conform to all of markdown. Are the examples on the Fountain documentation realistic ones that are causing you issues?