code: function injectCss(cssList, content) {
          var css = cssList.reduce(function (prev, now) {
              var uri = now.uri;
              return prev + '<link rel="stylesheet" type="text/css" href="' + uri + '">\r\n';
          }, '');
          if (content.indexOf(settings.styleTag) !== -1) {
              content = content.replace(settings.styleTag, css);
          }
          else {
              content = content.replace(/<\/head>/, css + '\n$&');
          }
          return content;
      }
docs: 页面中注入CSS资源引用
  @param cssList
  @param content
  @returns {XML|string|void}