importCss function
CSS's @import.
importCss("url('https://fonts.googleapis.com/css?family=Roboto')", 'screen');
Implementation
void importCss(String url, [String mediaQuery = '']) {
if (!url.startsWith(url) && !url.startsWith('"') && !url.startsWith("'")) {
url = '"$url"';
}
sheet.addFirst('@import $url $mediaQuery;');
}