now.json file with routing rules for a Create-React-App.

now.json

{
  "version": 2,
  "name": "jetztein",
  "alias": "jetztein.de",
  "builds": [{ "src": "package.json", "use": "@now/static-build" }],
  "regions": ["bru"],
  "routes": [
    { "src": "^/static/(.*)", "dest": "/static/$1" },
    { "src": "^/favicon.ico", "dest": "/favicon.ico" },
    { "src": "^/asset-manifest.json", "dest": "/asset-manifest.json" },
    { "src": "^/manifest.json", "dest": "/manifest.json" },
    { "src": "^/service-worker.js", "headers": { "cache-control": "s-maxage=0" }, "dest": "/service-worker.js" },
    { "src": "^/precache-manifest.(.*)", "dest": "/precache-manifest.$1" },
    { "src": "^/(.*)", "dest": "/index.html" }
  ]
}