Examine source code of Wowhead extras

{
  "manifest_version": 2,
  "name": "Wowhead extras",
  "description": "Adds extra features to wowhead",
  "version": "1.0.3",
  "browser_action": {
    "default_icon": "icon_128.png"
  },
  "icons": {
    "48": "icon_48.png",
    "128": "icon_128.png"
  },
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "https://*.wowhead.com/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2148a6c7-27be-4a41-a188-7136f7caf845}"
    }
  }
}