title: Access-Control-Allow-Origin added to firebase.json but missing from the file response header
body: <p>Below is my simple firebase.json. If I read the docs right it should tag all files with 'Access-Control-Allow-Origin'. Unfortunately none of the files are being tagged resulting in the error:</p>
  
  <blockquote>
    <p>Imported resource from origin '<a href="https://gaspush.firebaseapp.com" rel="noreferrer">https://gaspush.firebaseapp.com</a>' has
    been blocked from loading by Cross-Origin Resource Sharing policy: No
    'Access-Control-Allow-Origin' header is present on the requested
    resource.</p>
  </blockquote>
  
  <p>Could someone take a look and let me know how to properly allow all files to all endpoints?</p>
  
  <pre><code>{
    "firebase": "gaspush",
    "headers": [ {
      "source" : “**”,
      "headers" : [ {
        "key" : "Access-Control-Allow-Origin",
        "value" : "*"
      } ]
    } ],
    "public": ".",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ]
  }
  </code></pre>