Examine source code of SteGOG

{
  "manifest_version": 2,
  "name": "SteGOG",
  "version": "0.0.21",
  "description": "Display games owned on Steam in GOG",
  "icons": {
    "48": "icons/stegog-48.png",
    "128": "icons/stegog-128.png"
  },
  "options_ui": {
    "page": "src/options.html"
  },
  "permissions": [
    "*://api.steampowered.com/*",
    "*://api.isthereanydeal.com/*",
    "storage"
  ],
  "background": {
    "scripts": [
      "lib/bluebird.min.js",
      "lib/browser-polyfill.min.js",
      "src/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.gog.com/*"
      ],
      "js": [
        "lib/bluebird.min.js",
        "lib/browser-polyfill.min.js",
        "lib/lodash.min.js",
        "src/stegog.js"
      ],
      "css": [
        "src/stegog.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "stegog@ugzuzg.com.amo"
    }
  },
  "web_accessible_resources": [
    "images/g99.png"
  ]
}