code: function createNormalRu( $rb, $rt, attr ) {
    var $ru = $.create( 'h-ru' )
    var $rt = $.clone( $rt )
    var attr = attr || {}
    attr.annotation = 'true'
  
    if ( Array.isArray( $rb )) {
      $ru.innerHTML = $rb.map(function( rb ) {
        if ( typeof rb === 'undefined' )  return ''
        return rb.outerHTML
      }).join('') + $rt.outerHTML
    } else {
      $ru.appendChild( $.clone( $rb ))
      $ru.appendChild( $rt )
    }
  
    $.setAttr( $ru, attr )
    return $ru
  }
docs: Create and return a new `<h-ru>` element
  according to the given contents