Examine source code of WatchJs

{
  "manifest_version": 2,
  "name": "WatchJs",
  "version": "1.0",
  "description": "List all JavaScript files loaded by a website",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a553b891-19f8-4e22-87d6-a09b46fab0a6}"
    }
  }
}