Examine source code of Duplicated Tabs Destroyer

{
  "manifest_version": 2,
  "name": "Duplicated Tabs Destroyer",
  "version": "1.5",
  "description": "Get rid of any duplicated tabs you have open in your browser.",
  "homepage_url": "https://github.com/dharmadeveloper108/firefox-extensions/tree/master/duplicated-tabs-destroyer",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "browser_style": true,
    "default_title": "Duplicated Tabs Destroyer",
    "default_popup": "kaboom.html"
  },
  "icons": {
    "48": "icons/kaboom.png"
  }
}