Examine source code of CertBadger

{
  "manifest_version": 2,
  "name": "CertBadger",
  "version": "0.1.1",
  "description": "Displays a badge for TLS/SSL certificates expiring soon.",
  "browser_specific_settings": {
    "gecko": {
      "id": "addon@certbadger"
    }
  },
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking",
    "https://*/*"
  ],
  "icons": {
    "48": "icons/certbadger.svg"
  },
  "browser_action": {
    "default_icon": "icons/toolbar.svg",
    "default_title": "CertBadger",
    "default_popup": "ui/cert_list.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "ui/options.html"
  }
}