scrollToBottom 渲染前获取并设置高度bug

[wvq]

vue3-virtual-scroll-list/src/virtual-list.tsx

Lines 256 to 271 in 1a60766

	const scrollToBottom = () => {
	if (shepherd.value) {
	const offset =
	shepherd.value[isHorizontal ? 'offsetLeft' : 'offsetTop'];
	scrollToOffset(offset);
	// check if it's really scrolled to the bottom
	// maybe list doesn't render and calculate to last range
	// so we need retry in next event loop until it really at bottom
	setTimeout(() => {
	if (getOffset() + getClientSize() < getScrollSize()) {
	scrollToBottom();
	}
	}, 3);
	}
	};

这里3ms不够，可能在渲染新数据完成前获取高度。

参考 https://developer.mozilla.org/zh-CN/docs/Web/API/Window/requestAnimationFrame

一般情况每秒60次回调，就是17ms回调一次，设置成大于17ms的值才行。
页面比较卡的时候还是会有问题，以下写法更稳妥点:

const scrollToBottom = () => {
      if (shepherd.value) {
        requestAnimationFrame(() => {
          requestAnimationFrame(() => {
            scrollToOffset(shepherd.value[isHorizontal ? 'offsetLeft' : 'offsetTop'])
          })
        })
      }
    }

#13 的问题也一并解决了