Examine source code of Backpack

{
  "manifest_version": 2,
  "name": "Backpack",
  "version": "5.5",
  "description": "Backpack",
  "browser_action": {
    "default_icon": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2b8e5a2d-d223-4373-bdd8-142b3b4784d1}"
    }
  }
}