code: function compile(wxss, options = {}) {
    if (options.less) {
      less.render(wxss, (err, output) => {
        if (!err) wxss = output.css
      })
    }
  
    wxss = postcss([addClassPrefixPlugin(options.prefix)]).process(wxss, {
      from: undefined, // 主要是不想看到那个 warning
      map: null,
    }).css
  
    // 压缩
    return csso.minify(wxss, {restructure: false}).css
  }
docs: 编译 wxss