使用图片预加载与背景图占位解决图片请求失败问题

https://github.com/SusieChang/react-app/blob/12be621e34fd822603e3325b1b44c09fa9080759/src/components/LazyImg/index.js#L14-L30

问题 React-hooks. Can't perform a React state update on an unmounted component 的[解决方案](https://stackoverflow.com/questions/56442582/react-hooks-cant-perform-a-react-state-update-on-an-unmounted-component/56443045#56443045)