在Angular中，可以通过自定义配置文件来手动添加manifest.webmanifest的服务。以下是一种可能的解决方法：

1. 在项目的根目录中创建一个名为manifest.webmanifest的文件，并将以下示例代码复制到该文件中：

{
  "name": "My Angular App",
  "short_name": "My App",
  "start_url": "./index.html",
  "display": "standalone",
  "background_color": "#ffffff",
  "theme_color": "#f44336",
  "icons": [
    {
      "src": "assets/icons/icon-72x72.png",
      "sizes": "72x72",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-96x96.png",
      "sizes": "96x96",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-128x128.png",
      "sizes": "128x128",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-144x144.png",
      "sizes": "144x144",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-152x152.png",
      "sizes": "152x152",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-192x192.png",
      "sizes": "192x192",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-384x384.png",
      "sizes": "384x384",
      "type": "image/png"
    },
    {
      "src": "assets/icons/icon-512x512.png",
      "sizes": "512x512",
      "type": "image/png"
    }
  ]
}

2. 打开angular.json文件，并在"assets"数组中添加manifest.webmanifest文件的路径，例如：

"assets": [
  "src/favicon.ico",
  "src/assets",
  "src/manifest.webmanifest"
]

3. 在src/index.html文件中，添加以下代码片段，将manifest.webmanifest文件链接到HTML文件中：

4. 重新运行Angular应用程序，manifest.webmanifest文件将被添加到构建的输出目录中，并且可以通过https://your-domain/manifest.webmanifest访问。

请注意，上述示例代码中的图标路径是相对于项目的根目录。如果您的图标位于不同的目录中，请相应地更新图标的路径。