Examine source code of Manganelo arrow key

{
  "manifest_version": 2,
  "name": "Next Chapter Button Clicker",
  "version": "1.0",
  "description": "Automatically clicks the 'NEXT CHAPTER' button",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://chapmanganelo.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "activeTab",
    "https://chapmanganelo.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3c95a554-c13c-4f8a-abca-625a3d45b942}"
    }
  }
}