Examine source code of Curious Web

{
  "manifest_version": 2,
  "name": "Curious Web",
  "version": "1.0",
  "description": "Adds a '?' to every heading tag on webpages.",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Add question marks to headings",
    "default_icon": {
      "16": "icon16-disabled.png",
      "32": "icon32-disabled.png",
      "48": "icon48-disabled.png",
      "128": "icon128-disabled.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ccdb4335-66c6-4431-80a6-c5d26a857ee8}"
    }
  }
}