Examine source code of your-phone.net

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "short_name": "__MSG_extensionName__",
  "version": "0.0.6resigned1",
  "default_locale": "de",
  "description": "__MSG_extensionDescription__",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "jquery-3.3.1.min.js",
        "sibphone.js"
      ],
      "css": [
        "style.css"
      ]
    }
  ],
  "applications": {
    "gecko": {
      "id": "sibphone@your-phone.net"
    }
  },
  "icons": {
    "16": "icons/sibphone-logo-quad-16.png",
    "48": "icons/sibphone-logo-quad-48.png",
    "128": "icons/sibphone-logo-quad-128.png"
  }
}