website/ngsw-config.json

{
  "index": "/index.html",
  "assetGroups": [
    {
      "name": "app",
      "installMode": "prefetch",
      "resources": {
        "files": ["/index.html", "/*.css", "/*.js"]
      }
    },
    {
      "name": "assets",
      "installMode": "lazy",
      "updateMode": "prefetch",
      "resources": {
        "files": ["/assets/**"]
      }
    },
    {
      "name": "external assets",
      "installMode": "prefetch",
      "updateMode": "prefetch",
      "resources": {
        "urls": [
          "https://use.fontawesome.com/releases/v5.1.0/css/all.css",
          "https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css",
          "https://fonts.googleapis.com/**"
        ]
      }
    }
  ]
}