Support config setting "Preferred Line Length" on a per-rule basis

[dzliergaard]

I would love to be able to set a different wrap limit for each rule in a grammar dictionary. I'm using the fountain package to write a screenplay which has different margins based on rules. I am working on using css to get the display the way I want, but the line numbers are going to be all off if I can't have it soft-wrap directly and have to use white-space css instead.