Examine source code of Timed Mute

{
  "applications": {
    "gecko": {
      "strict_min_version": "58.0a1",
      "id": "{03b4196b-fac1-4f62-aaf9-5ca1f429a0d7}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "Timed Mute"
  },
  "icons": {
    "48": "icon-grey.svg",
    "96": "icon-grey.svg"
  },
  "description": "After X amount of time mute the tab.",
  "manifest_version": 2,
  "name": "Timed Mute",
  "permissions": [
    "tabs"
  ],
  "version": "1.2resigned1"
}