Parse less and scss files

This pull request is for [Simple support for LESS/SCSS](https://trello.com/c/KoK6kPtp/1190-m-simple-support-for-less-scss-in-key-brackets-features).


This was patterned after the other Live Preview documents, which *all* need JSDoc reviews. I'm ok without JSDoc updates to make sure this gets in to 0.43