Examine source code of Wikipedia Grade Icon

{
  "manifest_version": 3,
  "name": "Wikipedia Add Class Icon",
  "version": "1.4.1",
  "description": "Displays the grade of a Wikipedia article.",
  "icons": {
    "48": "assets/Symbol_b_class.svg",
    "96": "assets/Symbol_b_class.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "https://en.wikipedia.org/wiki/*",
        "https://en.m.wikipedia.org/wiki/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "wikipedia-add-class-icon@zachglindro.com"
    },
    "gecko_android": {}
  }
}