Examine source code of Replay - Watch Time Tracker

{
  "manifest_version": 3,
  "name": "Replay",
  "version": "0.3.0",
  "description": "See exactly where your YouTube hours go — by channel and category. Accurate, private, and 100% on your device.",
  "browser_specific_settings": {
    "gecko": {
      "id": "replay@ricardo.dev",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "permissions": [
    "storage",
    "notifications"
  ],
  "host_permissions": [
    "https://www.youtube.com/*"
  ],
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg",
    "128": "icons/icon.svg"
  },
  "background": {
    "scripts": [
      "stats.js",
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon.svg",
    "default_title": "Replay"
  }
}