Examine source code of Tab Cleanup Suggester

{
  "manifest_version": 2,
  "name": "Tab Cleanup Suggester",
  "version": "1.0",
  "description": "Suggest unused tabs to close.",
  "permissions": [
    "tabs",
    "idle"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{11a4735a-149a-41ae-a9a8-2f83f2b97df0}"
    }
  }
}