Examine source code of Redirect Checker

{
  "browser_specific_settings": {
    "gecko": {
      "id": "serge@designwalthamstow.co.uk"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "assets/images/ricon19_off.png",
    "default_popup": "popup.html",
    "default_title": "Click here to check for redirects."
  },
  "content_scripts": [
    {
      "js": [
        "metaRefreshDetect.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start"
    }
  ],
  "description": "HTTP Header & Redirect Checker for SEO",
  "icons": {
    "16": "assets/images/ricon16.png",
    "48": "assets/images/ricon48.png",
    "128": "assets/images/ricon128.png"
  },
  "manifest_version": 2,
  "name": "Redirect Checker",
  "permissions": [
    "webRequest",
    "webNavigation",
    "<all_urls>",
    "clipboardWrite"
  ],
  "version": "1.0"
}