firebase.json

{
  "hosting": [
    {
      "target": "production",
      "public": "build",
      "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
      "rewrites": [
        {
          "source": "/robots.txt",
          "destination": "/robots.staging.txt"
        },
        {
          "source": "/components/**",
          "destination": "/components/index.html"
        },
        {
          "source": "**",
          "destination": "/index.html"
        }
      ]
    },
    {
      "target": "staging",
      "public": "build",
      "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
      "rewrites": [
        {
          "source": "/robots.txt",
          "destination": "/robots.staging.txt"
        },
        {
          "source": "/components/**",
          "destination": "/components/index.html"
        },
        {
          "source": "**",
          "destination": "/index.html"
        }
      ]
    }
  ],
  "emulators": {
    "hosting": {
      "port": 4444
    },
    "ui": {
      "enabled": true
    }
  }
}