expose wrap/unwrap CSS functions

In https://github.com/cfware/babel-plugin-template-html-minifier we are using `html-minifier` but require a special handling for minifying CSS. We'd like to preserve `html-minifier`'s logic for handling minification of inline and css and media queries.

Is it possible to provide these functions as public exports, so that they can be reused? https://github.com/kangax/html-minifier/blob/gh-pages/src/htmlminifier.js#L358

See the tracking issue here https://github.com/cfware/babel-plugin-template-html-minifier/issues/30

Start at src/htmlminifier.js around line 358, linked from the issue, and inspect how the CSS wrap/unwrap functions are defined and exported. Done means the functions are publicly reusable without breaking existing inline CSS and media-query minification behavior; verify with the repository's existing checks.

Written by the indexing model from the issue text.