Examine source code of rolltwenty-page-fixer

{
  "manifest_version": 2,
  "name": "rolltwenty-page-fixer",
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "https://app.roll20.net/campaigns/chatarchive/*"
      ],
      "js": [
        "pagefixer.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9fe2c190-4ba7-4646-84f4-6186b2f77bfd}"
    }
  }
}