Examine source code of Youtube AdMute

{
  "manifest_version": 2,
  "name": "YT-AdMute",
  "version": "1.9.4resigned1",
  "description": "Automatically mute and skip ads on Youtube",
  "icons": {
    "48": "ytvm_icon_48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "ytvm.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6538f546-ec7b-4020-b5c2-a14a333367a7}"
    }
  }
}