Examine source code of YouTube Live Clock

{
  "manifest_version": 3,
  "name": "YouTube Live Clock",
  "version": "2.1",
  "description": "Shows stream duration next to LIVE badge on YouTube",
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "menarchiveclips@gmail.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "host_permissions": [
    "*://www.youtube.com/*",
    "*://youtube.com/*"
  ]
}