Examine source code of Zoomer - Zoom Manager

{
  "manifest_version": 2,
  "name": "Zoomer - Zoom Manager",
  "version": "1.3",
  "description": "Set and remember custom zoom levels per web-site.",
  "icons": {
    "48": "48.png",
    "64": "64.png",
    "96": "96.png",
    "128": "128.png"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "64.png",
    "default_popup": "popup.html",
    "default_title": "Zoom Manager"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fd845a54-9476-463b-b43d-61678edc83db}",
      "strict_min_version": "114.0"
    }
  }
}