app.vue style部分添加以下内容：
.el-dialog { display: flex !important; flex-direction: column !important; margin: 0 !important; position: absolute !important; top: 50% !important; left: 50% !important; transform: translate(-50%, -50%) !important; overflow-y: scroll !important; max-height: 100vh !important; }
之后的效果：dialog上下左右在视口居中、过长body不在出现滚动条，开启内滚动（dialog最高100vh）
