Examine source code of Auto Tab Closer

{
  "manifest_version": 2,
  "name": "Auto Tab Closer",
  "version": "1.0.5",
  "description": "Arc-style tab closing for Firefox",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "alarms",
    "sessions",
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_title": "Tab Closer",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "auto-tab-closer@koman.app",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "strict_min_version": "142.0"
    }
  }
}