Examine source code of Tubemark

{
  "manifest_version": 3,
  "name": "Tubemark",
  "description": "Tracks YouTube videos you watch and resumes from where you left off",
  "version": "1.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "tubemark@johnykosmos.com"
    }
  },
  "permissions": [
    "storage"
  ],
  "icons": {
    "48": "icons/icon48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles/contentstyle.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "action": {
    "default_title": "Tubemark",
    "default_popup": "popup.html"
  }
}