Examine source code of Sound changer

{
  "manifest_version": 2,
  "name": "Sound changer",
  "version": "1.0",
  "description": "A simple extension that controls sound per tab",
  "icons": {
    "48": "icons/unmute.png"
  },
  "permissions": [
    "tabs",
    "activeTab",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/unmute.png",
    "default_title": "My Extension",
    "default_popup": "popup.html"
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{7463d5e7-e9d9-47de-954a-7b136d8d7509}"
    }
  }
}