Examine source code of Simple GitHub Bookmark

{
  "description": "Adds browser action icon to toolbar to open the GitHub web page.",
  "manifest_version": 2,
  "name": "open-github",
  "version": "1.0",
  "icons": {
    "48": "icons/favicon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/favicon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{617b7a04-e467-440a-b3b3-73637a36ed60}"
    }
  }
}