Examine source code of Unduplify

{
  "manifest_version": 2,
  "name": "unduplify",
  "version": "1.0",
  "description": "Remove all duplicate tabs, leaving only 1 instance of each link.",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/beastify",
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Unduplify"
  },
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}