Examine source code of Brightness Control

{
  "manifest_version": 2,
  "name": "Brightness Control",
  "version": "1.0",
  "description": "Freely control the brightness of your web page",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "/content_script.js"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "48": "/icon.png"
    },
    "default_title": "Brightness Control",
    "default_popup": "/popup.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2bfaccdf-d97a-4a9a-9e66-d09aef4edd6c}"
    }
  }
}