Examine source code of Promo Alert

{
  "manifest_version": 2,
  "name": "Promo Alert",
  "version": "1.0.1",
  "description": "Searches Latest Promotions, Discounts and Coupons on websites you visit and shows you notifications if any found",
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "icon.png"
  },
  "background": {
    "scripts": [
      "background1.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentscript1.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "PromoAlert@enhancedbrowsing.com"
    }
  }
}