Map url() calls. Replace all url()s using a given function.
$ npm install --save rework-plugin-urlvar css = rework(read(css))
.use(rework.url(function(url){
return 'http://example.com' + url;
}))
.toString()body {
background: url(/images/bg.png);
}yields:
body {
background: url(http://example.com/images/bg.png);
}