firebase.json

{
  "hosting": {
    "site": "freechess",
    "public": "out",
    "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
    "cleanUrls": true,
    "trailingSlash": false,
    "predeploy": ["npm run lint", "npm run build"],
    "headers": [
      {
        "source": "/",
        "headers": [
          {
            "key": "Cross-Origin-Embedder-Policy",
            "value": "require-corp"
          },
          {
            "key": "Cross-Origin-Opener-Policy",
            "value": "same-origin"
          }
        ]
      },
      {
        "source": "/engines/**",
        "headers": [
          {
            "key": "Cross-Origin-Embedder-Policy",
            "value": "require-corp"
          },
          {
            "key": "Cross-Origin-Opener-Policy",
            "value": "same-origin"
          },
          {
            "key": "Cache-Control",
            "value": "public, max-age=31536000, immutable"
          }
        ]
      },
      {
        "source": "/play",
        "headers": [
          {
            "key": "Cross-Origin-Embedder-Policy",
            "value": "require-corp"
          },
          {
            "key": "Cross-Origin-Opener-Policy",
            "value": "same-origin"
          }
        ]
      },
      {
        "source": "/database",
        "headers": [
          {
            "key": "Cross-Origin-Embedder-Policy",
            "value": "require-corp"
          },
          {
            "key": "Cross-Origin-Opener-Policy",
            "value": "same-origin"
          }
        ]
      }
    ]
  }
}