Examine source code of Auto Mute Site

{
  "author": "igorlogius",
  "homepage_url": "https://github.com/igorlogius/mute-origin",
  "browser_action": {
    "default_area": "navbar"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "474": "icon.png"
  },
  "manifest_version": 2,
  "name": "Mute Origin",
  "description": "Mute Tabs by Origin (aka. Site / Proto+Domain+Port)",
  "permissions": [
    "storage",
    "tabs"
  ],
  "version": "1.0.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{b481a762-810d-46d1-a5fe-ae01d51700f6}"
    }
  }
}