Examine source code of iframe auto opener

{
  "manifest_version": 3,
  "name": "Automatic Iframe Opener",
  "version": "1.5",
  "description": "Redirects to single iframes and uses Alt+Shift+I to toggle between page and iframe.",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "iframe-auto-opener@sky.yy",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {},
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Alt+Shift+I",
        "linux": "Alt+Shift+I"
      },
      "description": "Toggle between the original webpage and the iframe"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://learn.canterbury.ac.nz/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ]
}