Extend `prettier` formatter to handle line range
Extend `prettier` formatter to handle line range

Way more complicated than it seemed like it should be, since the offsets
are character-based (and not line- or byte-based).

benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles