Examine source code of grank.fun

{
  "manifest_version": 2,
  "name": "grank.xyz",
  "version": "1.2",
  "description": "A way to rate games out of 10 on the Steam Store.",
  "permissions": [
    "storage",
    "https://api.grank.xyz/*",
    "https://openid.grank.xyz/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://store.steampowered.com/app/*",
        "https://grank.xyz/*",
        "https://www.grank.xyz/*"
      ],
      "js": [
        "main.js"
      ],
      "css": [
        "main.css"
      ]
    }
  ],
  "icons": {
    "16": "icons/logo16.png",
    "48": "icons/logo48.png",
    "128": "icons/logo128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2f347d67-36a3-42c8-95bc-07abd5bb4ee0}"
    }
  }
}