allow options to be set for line commenting

This allows line commenting to take [addon options](https://github.com/marijnh/CodeMirror/blob/master/addon/comment/comment.js). Specifically, I wanted to have [my comments indented](https://github.com/cldwalker/ltfiles/blob/eb65c4a3f6d7010caabf60119d4e12306db3dd4f/src/lt/plugins/ltfiles/vim.cljs#L36-L47) while in clojure. I could also add a default of `{:indent true}` to the Clojure plugin if desired.