Examine source code of Arkivalieronline+

{
  "manifest_version": 2,
  "name": "Arkivalieronline+",
  "version": "1.0.2",
  "description": "Tilføjer forbedringer til Rigsarkivets Arkivalieronline.",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://arkivalieronline.rigsarkivet.dk/*"
      ],
      "js": [
        "arkivalieronline-plus.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7340505b-f4d1-45e8-899d-af4e2ddb441a}"
    }
  }
}