Examine source code of YouTube Timestamp Marker

{
  "manifest_version": 3,
  "name": "YouTube Marker",
  "version": "1.0",
  "description": "Adds marking buttons directly to the YouTube control bar.",
  "browser_specific_settings": {
    "gecko": {
      "id": "youtube-marker@yourname.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "48": "Icon-48.png",
    "96": "Icon-96.png",
    "128": "Icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/watch*"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}