[@ant-design/icons-angular]: the icon caret-down-o does not exist in your assets folder.
解决办法：在 angular.json 文件中引入样式和 SVG icon 资源。
{
"assets": [
...
{
"glob": "**/*",
"input": "./node_modules/@ant-design/icons-angular/src/inline-svg/",
"output": "/assets/"
}
],
"styles": [
...
"node_modules/ng-zorro-antd/ng-zorro-antd.min.css"
]
}
