Examine source code of AO3 arrow navigation

{
  "manifest_version": 3,
  "version": "1.0",
  "name": "AO3 arrow navigation",
  "permissions": [],
  "host_permissions": [
    "https://archiveofourown.org/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://archiveofourown.org/*"
      ],
      "js": [
        "nav.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "ao3_navigator@akif.dev"
    }
  },
  "action": {
    "default_icon": "images/icon.png"
  },
  "icons": {
    "16": "images/icon.png",
    "48": "images/icon.png",
    "128": "images/icon.png"
  }
}