firebase.json

{
  "database": {
    "rules": "database.rules.json"
  },
  "hosting": {
    "public": "docs",
    "ignore": ["firebase.json", "**/.*"],
    "headers": [
      {
        "source": "**",
        "headers": [
          { "key": "X-Frame-Options", "value": "DENY" },
          { "key": "X-Content-Type-Options", "value": "nosniff" },
          { "key": "Referrer-Policy", "value": "strict-origin-when-cross-origin" },
          { "key": "Content-Security-Policy", "value": "default-src 'self'; script-src 'self' 'unsafe-inline' https://www.gstatic.com https://unpkg.com https://apis.google.com https://*.firebasedatabase.app; style-src 'self' 'unsafe-inline' https://unpkg.com https://fonts.googleapis.com; img-src 'self' data: https://*.tile.openstreetmap.org https://*.basemaps.cartocdn.com; connect-src 'self' https://*.firebasedatabase.app wss://*.firebasedatabase.app https://*.googleapis.com https://www.gstatic.com https://unpkg.com https://identitytoolkit.googleapis.com https://securetoken.googleapis.com; font-src 'self' https://fonts.gstatic.com; frame-src https://*.firebaseapp.com https://apis.google.com https://*.firebasedatabase.app; frame-ancestors 'none'" }
        ]
      }
    ]
  }
}