Examine source code of Reply Guard

{
  "manifest_version": 3,
  "name": "Reply Guard",
  "version": "1.0.0",
  "description": "Guards reply buttons on Gmail conversations with the 'Reply Guard' label",
  "browser_specific_settings": {
    "gecko": {
      "id": "reply-guard@nitz",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {}
}