Examine source code of Frequency Generator Pro

{
  "manifest_version": 2,
  "name": "Frequency Generator",
  "description": "Generate audio tones of any frequency.",
  "version": "1.2",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "web_accessible_resources": [
    "popup.html",
    "background.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5e4d9ecf-835a-4090-ae5b-b5a36670f2d2}"
    }
  }
}