[BUG] force layout issue

[gaokun]

Hi,

There is a bug in 'updated' on Vue3 version

updated(el, binding, vnode, oldVnode) {
    var inserted = false;
    for (var i = 0, length = el.children; i < length; i++) {
      if (el.children[i] === el.__resizeTrigger__) {
        inserted = true;
      }
    }
    if (!inserted) {
      var _isIE = isIE();
      _isIE && el.appendChild(el.__resizeTrigger__);
      el.__resizeTrigger__.data = "about:blank";
      !_isIE && el.appendChild(el.__resizeTrigger__);
    }
  },

length = el.children should be length = el.children.length

See here: resize-observer-directive.js L159

[gaokun]

@wangweiwei Plz help to check the PR