Examine source code of Outlook Button

{
  "description": "Open Outlook Button",
  "manifest_version": 2,
  "name": "Outlook Button",
  "version": "1.4",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/mail-16.png",
      "24": "icons/mail-24.png",
      "32": "icons/mail-32.png",
      "48": "icons/mail-48.png",
      "64": "icons/mail-64.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{712a0bac-e801-4331-9ebb-20b6b3d79d4f}"
    }
  }
}