firebase.json

{
"hosting":
{
  "firebase": "readium",
  "public": "./dist/cloud-reader",
  "ignore": [
    "firebase.json",
    "**/.*",
    "**/node_modules/**"
  ],
  "headers": [
    {
      "source": "epub_content/**",
      "headers": [
        {
          "key": "Access-Control-Allow-Origin",
          "value": "*"
        },
        {
          "key": "Access-Control-Allow-Methods",
          "value": "GET, HEAD, OPTIONS"
        },
        {
          "key": "Access-Control-Allow-Headers",
          "value": "Content-Type, Content-Length, Accept-Ranges, Content-Range, Range, Link, Transfer-Encoding"
        },
        {
          "key": "Access-Control-Expose-Headers",
          "value": "Content-Type, Content-Length, Accept-Ranges, Content-Range, Range, Link, Transfer-Encoding"
        }
      ]
    }
  ]
}
}