Handle SASS debug info

CSS compiled by SASS has a debug info declaration which has nested braces. This commit makes the regex consume the second closing brace so it doesn't get parsed as part of the following selector.

E.g.
```css
@media -sass-debug-info{filename{font-family:file\:\/\/\/Users\/turadg\/Code\/Ruby\/app-rails\/app\/assets\/stylesheets\/objectives\/objectives\.css\.scss}line{font-family:\000032}}body.objectives.show #sidebar {  top: 15px;  position: sticky; }
````

was causing DOM error 12 because `parse(css)` was passing `}body.objectives.show #sidebar` to `qSA` (querySelectorAll).