Examine source code of List All Tabs

{
  "applications": {
    "gecko": {
      "strict_min_version": "58.0a1",
      "id": "{49dfc553-ba10-49f8-8d11-fc6579eaafa8}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "List All Tabs"
  },
  "description": "List tabs, find duplicates, and close them.",
  "homepage_url": "https://github.com/davidlazar/list-all-tabs",
  "manifest_version": 2,
  "name": "List All Tabs",
  "permissions": [
    "tabs"
  ],
  "version": "0.2resigned1"
}