Added .sjs extension to filter

sweet.js officially supports either `.js` or the more formal `.sjs` extension.

##### References
https://github.com/mozilla/sweet.js/blob/08e4392b4e821ac1a4d19bc70ff792ad58336f32/src/sweet.js#L188
https://github.com/search?q=extension%3Asjs+macro&ref=searchresults&type=Code