Examine source code of Paywall Sentry

{
  "name": "Paywall Sentry",
  "description": "Show alerts on search results that contain content locked behind a paywall or subscription fee.",
  "version": "0.1.0",
  "manifest_version": 2,
  "browser_action": {},
  "icons": {
    "16": "img/ps-icon16.png",
    "32": "img/ps-icon32.png",
    "48": "img/ps-icon48.png",
    "128": "img/ps-icon128.png"
  },
  "permissions": [
    "storage",
    "https://*.google.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "chrome_style": true
  },
  "web_accessible_resources": [
    "img/ps-icon16.png",
    "img/ps-icon32.png",
    "img/ps-icon48.png",
    "img/ps-icon128.png",
    "options.html",
    "background.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a2182b34-d9fe-4641-88f3-421a7eef4d6f}"
    }
  }
}