Easier error displaying

[passhley]

When a story errors, if we could somehow grab a block of the files source code to display and then highlight the error'd line somewhere in the previewer, that'd be a huge thing for newer developers. It was one of my most requested features when I was working on it.

[passhley]

Regarding this, I figured out about ScriptContext.Error:Connect which can produce an error and also passes the file that errored. However, I'm unsure how we could highlight the line that errors as I don't see anywhere that passes the line number. Our best shot would to be somehow grab it from the stack trace or something. If you could look deeper into this in hopes of possibly finding something, that'd be great!