code: function listSearchPaths(output) {
      var book = output.getBook();
      var plugins = output.getPlugins();
  
      var searchPaths = plugins
          .valueSeq()
          .map(function(plugin) {
              return plugin.getPath();
          })
          .toList();
  
      return searchPaths.unshift(book.getContentRoot());
  }
docs: List search paths for templates / i18n, etc
  
  @param {Output} output
  @return {List<String>}