Examine source code of Tab Expiry Timer

{
  "manifest_version": 2,
  "name": "Tab Expiry Timer",
  "version": "1.0",
  "description": "Set a timer on a tab; when time's up the tab closes automatically.",
  "icons": {
    "48": "icons/icon48.svg",
    "128": "icons/icon128.svg"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "browser_action": {
    "default_title": "Tab Expiry Timer",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b3dd488c-a6ac-4737-91e3-c5e90ac05ed1}"
    }
  }
}