https://medium.com/@remarkablemark/how-to-deploy-a-parcel-build-to-heroku-fa1ea74d2b96

static.json

{
  "root": "dist/",
  "routes": {
    "**": "index.html"
  },
  "https_only": true,
  "error_page": "index.html",
  "headers": {
    "/**": {
      "Cache-Control": "public, max-age=0, must-revalidate"
    },
    "/**.css": {
      "Cache-Control": "public, max-age=31536000, immutable"
    },
    "/**.ico": {
      "Cache-Control": "public, max-age=31536000, immutable"
    },
    "/**.jpg": {
      "Cache-Control": "public, max-age=31536000, immutable"
    },
    "/**.jpeg": {
      "Cache-Control": "public, max-age=31536000, immutable"
    },
    "/**.js": {
      "Cache-Control": "public, max-age=31536000, immutable"
    },
    "/**.png": {
      "Cache-Control": "public, max-age=31536000, immutable"
    }
  }
}